chapter 3 transport layer - simon fraser university€¦ · transport layer. 3-1. chapter 3...

Transport Layer 3-1

Chapter 3Transport Layer

Computer Networking A Top Down Approach 5th edition Jim Kurose Keith RossAddison-Wesley April 2009

A note on the use of these ppt slidesWersquore making these slides freely available to all (faculty students readers) Theyrsquore in PowerPoint form so you can add modify and delete slides (including this one) and slide content to suit your needs They obviously represent a lot of work on our part In return for use we only ask the following

If you use these slides (eg in a class) in substantially unaltered form that you mention their source (after all wersquod like people to use our book)

If you post any slides in substantially unaltered form on a www site that you note that they are adapted from (or perhaps identical to) our slides and note our copyright of this material

Thanks and enjoy JFKKWR

All material copyright 1996-2010JF Kurose and KW Ross All Rights Reserved

Transport Layer 3-2

Chapter 3 Transport LayerOur goals

understand principles behind transport layer services

multiplexingdemultiplexingreliable data transferflow controlcongestion control

learn about transport layer protocols in the Internet

UDP connectionless transportTCP connection-oriented transportTCP congestion control

Transport Layer 3-3

Chapter 3 outline

31 Transport-layer services

32 Multiplexing and demultiplexing

33 Connectionless transport UDP

34 Principles of reliable data transfer

35 Connection-oriented transport TCP

segment structurereliable data transferflow controlconnection management

36 Principles of congestion control

37 TCP congestion control

Transport Layer 3-4

Transport services and protocolsprovide logical communicationbetween app processes running on different hoststransport protocols run in end systems

send side breaks app messages into segments passes to network layerrcv side reassembles segments into messages passes to app layer

more than one transport protocol available to apps

Internet TCP and UDP

applicationtransportnetworkdata linkphysical


Transport Layer 3-5

Transport vs network layer

network layer logical communication between hoststransport layer logical communication between processes

relies on enhances network layer services

Household analogy12 kids sending letters to

12 kidsprocesses = kidsapp messages = letters in envelopeshosts = housestransport protocol = Ann and Bill who demux to in-house siblingsnetwork-layer protocol = postal service

Transport Layer 3-6

Internet transport-layer protocols

reliable in-order delivery (TCP)

congestion control flow controlconnection setup

unreliable unordered delivery UDP

no-frills extension of ldquobest-effortrdquo IP

services not available delay guaranteesbandwidth guarantees


networkdata linkphysical







Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8

Multiplexingdemultiplexing

application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1

host 1 host 2 host 3

= process= socket

delivering received segmentsto correct socket

Demultiplexing at rcv hostgathering data from multiplesockets enveloping data with header (later used for demultiplexing)

Multiplexing at send host

Transport Layer 3-9

How demultiplexing workshost receives IP datagrams

each datagram has source IP address destination IP addresseach datagram carries 1 transport-layer segmenteach segment has source destination port number

host uses IP addresses amp port numbers to direct segment to appropriate socket

source port dest port

32 bits

applicationdata

(message)

other header fields

TCPUDP segment format

Transport Layer 3-10

Connectionless demultiplexing

recall create sockets with host-local port numbers

DatagramSocket mySocket1 = new DatagramSocket(12534)


recall when creating datagram to send into UDP socket must specify

(dest IP address dest port number)

when host receives UDP segment

checks destination port number in segmentdirects UDP segment to socket with that port number

IP datagrams with different source IP addresses andor source port numbers directed to same socket


Connectionless demux (cont)DatagramSocket serverSocket = new DatagramSocket(6428)

ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

SP provides ldquoreturn addressrdquo


Connection-oriented demux

TCP socket identified by 4-tuple

source IP addresssource port numberdest IP addressdest port number

recv host uses all four values to direct segment to appropriate socket

server host may support many simultaneous TCP sockets

each socket identified by its own 4-tuple

web servers have different sockets for each connecting client

non-persistent HTTP will have different socket for each request


Connection-oriented demux (cont)

ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Connection-oriented demux Threaded Web Server

clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline










UDP User Datagram Protocol [RFC 768]

ldquono frillsrdquo ldquobare bonesrdquo Internet transport protocolldquobest effortrdquo service UDP segments may be

lostdelivered out of order to app

connectionlessno handshaking between UDP sender receivereach UDP segment handled independently of others

Why is there a UDPno connection establishment (which can add delay)simple no connection state at sender receiversmall segment headerno congestion control UDP can blast away as fast as desired


UDP more

often used for streaming multimedia apps

loss tolerantrate sensitive

other UDP usesDNSSNMP

reliable transfer over UDP add reliability at application layer

application-specific error recovery


32 bits

Applicationdata

(message)

UDP segment format

length checksumLength in

bytes of UDPsegmentincluding

header


UDP checksum

Sendertreat segment contents as sequence of 16-bit integerschecksum addition (1rsquos complement sum) of segment contentssender puts checksum value into UDP checksum field

Receivercompute checksum of received segmentcheck if computed checksum equals checksum field value

NO - error detectedYES - no error detected But maybe errors nonetheless More later hellip

Goal detect ldquoerrorsrdquo (eg flipped bits) in transmitted segment


Internet Checksum ExampleNote when adding numbers a carryout from the most significant bit needs to be added to the resultExample add two 16-bit integers

1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes
Kurose and Ross forgot to say anything about wrapping the carry and adding it to low order bit


Chapter 3 outline










Principles of Reliable data transferimportant in app transport link layerstop-10 list of important networking topics

characteristics of unreliable channel will determine complexity of reliable data transfer protocol (rdt)








Reliable data transfer getting started

sendside

receiveside

rdt_send() called from above (eg by app) Passed data to

deliver to receiver upper layer

udt_send() called by rdtto transfer packet over

unreliable channel to receiver

rdt_rcv() called when packet arrives on rcv-side of channel

deliver_data() called by rdt to deliver data to upper


Reliable data transfer getting startedWersquoll

incrementally develop sender receiver sides of reliable data transfer protocol (rdt)consider only unidirectional data transfer

but control info will flow on both directionsuse finite state machines (FSM) to specify sender receiver

state1

state2

event causing state transitionactions taken on state transition

state when in this ldquostaterdquo next state

uniquely determined by next event

eventactions


Rdt10 reliable transfer over a reliable channel

underlying channel perfectly reliableno bit errorsno loss of packets

separate FSMs for sender receiversender sends data into underlying channelreceiver read data from underlying channel

Wait for call from above packet = make_pkt(data)

udt_send(packet)

rdt_send(data)extract (packetdata)deliver_data(data)

Wait for call from

below

rdt_rcv(packet)

sender receiver


Rdt20 channel with bit errorsunderlying channel may flip bits in packet

checksum to detect bit errorsthe question how to recover from errors

acknowledgements (ACKs) receiver explicitly tells sender that pkt received OKnegative acknowledgements (NAKs) receiver explicitly tells sender that pkt had errorssender retransmits pkt on receipt of NAK

new mechanisms in rdt20 (beyond rdt10)error detectionreceiver feedback control msgs (ACKNAK) rcvr-gtsender

How do humans recover from ldquoerrorsrdquoduring conversation







rdt20 FSM specification

Wait for call from above

sndpkt = make_pkt(data checksum)udt_send(sndpkt)

extract(rcvpktdata)deliver_data(data)udt_send(ACK)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt)

rdt_rcv(rcvpkt) ampamp isACK(rcvpkt)

udt_send(sndpkt)

rdt_rcv(rcvpkt) ampampisNAK(rcvpkt)

udt_send(NAK)

rdt_rcv(rcvpkt) ampamp corrupt(rcvpkt)

Wait for ACK or

NAK

Wait for call from

belowsender

receiverrdt_send(data)

Λ


rdt20 operation with no errors


snkpkt = make_pkt(data checksum)udt_send(sndpkt)




udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ


rdt20 error scenario






udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ


rdt20 has a fatal flaw

What happens if ACKNAK corruptedsender doesnrsquot know what happened at receivercanrsquot just retransmit possible duplicate

Handling duplicates sender retransmits current pkt if ACKNAK garbledsender adds sequence number to each pktreceiver discards (doesnrsquot deliver up) duplicate pkt

Sender sends one packet then waits for receiver response

stop and wait


rdt21 sender handles garbled ACKNAKs

Wait for call 0 from

above

sndpkt = make_pkt(0 data checksum)udt_send(sndpkt)

rdt_send(data)

Wait for ACK or NAK 0 udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||isNAK(rcvpkt) )


rdt_send(data)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp isACK(rcvpkt)

udt_send(sndpkt)



Wait forcall 1 from

above

Wait for ACK or NAK 1

ΛΛ


rdt21 receiver handles garbled ACKNAKs

Wait for 0 from below

sndpkt = make_pkt(NAK chksum)udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp not corrupt(rcvpkt) ampamphas_seq0(rcvpkt)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp has_seq1(rcvpkt)

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)




rdt_rcv(rcvpkt) ampamp (corrupt(rcvpkt)

sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)






rdt21 discussion

Senderseq added to pkttwo seq rsquos (01) will suffice Whymust check if received ACKNAK corrupted twice as many states

state must ldquorememberrdquo whether ldquocurrentrdquo pkt has 0 or 1 seq

Receivermust check if received packet is duplicate

state indicates whether 0 or 1 is expected pkt seq

note receiver can notknow if its last ACKNAK received OK at sender


rdt22 a NAK-free protocol

same functionality as rdt21 using ACKs onlyinstead of NAK receiver sends ACK for last pkt received OK

receiver must explicitly include seq of pkt being ACKed duplicate ACK at sender results in same action as NAK retransmit current pkt


rdt22 sender receiver fragments


above


rdt_send(data)

udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||

isACK(rcvpkt1) )

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp isACK(rcvpkt0)

Wait for ACK

0sender FSM

fragment


extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(ACK1 chksum)udt_send(sndpkt)


rdt_rcv(rcvpkt) ampamp (corrupt(rcvpkt) ||

has_seq1(rcvpkt))

udt_send(sndpkt)receiver FSM

fragment

Λ


rdt30 channels with errors and loss

New assumptionunderlying channel can also lose packets (data or ACKs)

checksum seq ACKs retransmissions will be of help but not enough

Approach sender waits ldquoreasonablerdquo amount of time for ACK retransmits if no ACK received in this timeif pkt (or ACK) just delayed (not lost)

retransmission will be duplicate but use of seq rsquos already handles thisreceiver must specify seq of pkt being ACKed

requires countdown timer


rdt30 sendersndpkt = make_pkt(0 data checksum)udt_send(sndpkt)start_timer

rdt_send(data)

Wait for

ACK0

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||isACK(rcvpkt1) )


above

sndpkt = make_pkt(1 data checksum)udt_send(sndpkt)start_timer

rdt_send(data)




stop_timerstop_timer

udt_send(sndpkt)start_timer

timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action


Performance of rdt30

rdt30 works but performance stinksex 1 Gbps link 15 ms prop delay 8000 bit packet

U sender utilization ndash fraction of time sender busy sending

U sender =

00830008

= 000027 L R RTT + L R

=

if RTT=30 msec 1KB pkt every 30 msec -gt 33kBsec thruput over 1 Gbps linknetwork protocol limits use of physical resources

dsmicrosecon8bps10bits8000

9 ===RLdtrans


rdt30 stop-and-wait operation

first packet bit transmitted t = 0

sender receiver

RTT

last packet bit transmitted t = L R

first packet bit arriveslast packet bit arrives send ACK

ACK arrives send next packet t = RTT + L R

U sender =

008 30008

= 000027 L R RTT + L R

=


Pipelined protocolspipelining sender allows multiple ldquoin-flightrdquo yet-to-

be-acknowledged pktsrange of sequence numbers must be increasedbuffering at sender andor receiver

two generic forms of pipelined protocols go-Back-N selective repeat


Pipelining increased utilization


sender receiver

RTT

last bit transmitted t = L R



last bit of 2nd packet arrives send ACKlast bit of 3rd packet arrives send ACK

U sender =

02430008

= 00008 3 L R RTT + L R

=

Increase utilizationby a factor of 3


Pipelined Protocols

Go-back-N big picturesender can have up to N unacked packets in pipelinercvr only sends cumulative acks

doesnrsquot ack packet if therersquos a gap

sender has timer for oldest unacked packet

if timer expires retransmit all unackrsquoed packets

Selective Repeat big picsender can have up to N unackrsquoed packets in pipelinercvr sends individual ack for each packetsender maintains timer for each unacked packet

when timer expires retransmit only unackrsquoed packet


Go-Back-NSender

k-bit seq in pkt headerldquowindowrdquo of up to N consecutive unackrsquoed pkts allowed

ACK(n) ACKs all pkts up to including seq n - ldquocumulative ACKrdquomay receive duplicate ACKs (see receiver)

timer for each in-flight pkttimeout(n) retransmit pkt n and all higher seq pkts in window


GBN sender extended FSM

Wait start_timerudt_send(sndpkt[base])udt_send(sndpkt[base+1])hellipudt_send(sndpkt[nextseqnum-1])

timeout

rdt_send(data)

if (nextseqnum lt base+N) sndpkt[nextseqnum] = make_pkt(nextseqnumdatachksum)udt_send(sndpkt[nextseqnum])if (base == nextseqnum)

start_timernextseqnum++

elserefuse_data(data)

base = getacknum(rcvpkt)+1If (base == nextseqnum)

stop_timerelsestart_timer


base=1nextseqnum=1


Λ


GBN receiver extended FSM

ACK-only always send ACK for correctly-received pkt with highest in-order seq

may generate duplicate ACKsneed only remember expectedseqnum

out-of-order pkt discard (donrsquot buffer) -gt no receiver bufferingRe-ACK pkt with highest in-order seq

Wait

udt_send(sndpkt)default

rdt_rcv(rcvpkt)ampamp notcurrupt(rcvpkt)ampamp hasseqnum(rcvpktexpectedseqnum)

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(expectedseqnumACKchksum)udt_send(sndpkt)expectedseqnum++

expectedseqnum=1sndpkt = make_pkt(expectedseqnumACKchksum)

Λ


GBN inaction


Selective Repeat

receiver individually acknowledges all correctly received pkts

buffers pkts as needed for eventual in-order delivery to upper layer

sender only resends pkts for which ACK not received

sender timer for each unACKed pktsender window

N consecutive seq rsquosagain limits seq s of sent unACKrsquoed pkts


Selective repeat sender receiver windows


Selective repeat

data from above if next available seq in window send pkt

timeout(n)resend pkt n restart timer

ACK(n) in [sendbasesendbase+N]

mark pkt n as receivedif n smallest unACKed pkt advance window base to next unACKed seq

senderpkt n in [rcvbase rcvbase+N-1]

send ACK(n)out-of-order bufferin-order deliver (also deliver buffered in-order pkts) advance window to next not-yet-received pkt

pkt n in [rcvbase-Nrcvbase-1]

ACK(n)otherwise

ignore

receiver


Selective repeat in action


Selective repeatdilemma

Example seq rsquos 0 1 2 3window size=3

receiver sees no difference in two scenariosincorrectly passes duplicate data as new in (a)

Q what relationship between seq size and window size


Chapter 3 outline










TCP Overview RFCs 793 1122 1323 2018 2581

full duplex databi-directional data flow in same connectionMSS maximum segment size

connection-orientedhandshaking (exchange of control msgs) inits sender receiver state before data exchange

flow controlledsender will not overwhelm receiver

point-to-pointone sender one receiver

reliable in-order byte steam

no ldquomessage boundariesrdquopipelined

TCP congestion and flow control set window size

send amp receive buffers

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

applicationwrites data

applicationreads data


TCP segment structure


32 bits

applicationdata

(variable length)

sequence numberacknowledgement number

Receive windowUrg data pnterchecksum

FSRPAUheadlen

notused

Options (variable length)

URG urgent data (generally not used)

ACK ACK valid

PSH push data now(generally not used)

RST SYN FINconnection estab(setup teardown

commands)

bytes rcvr willingto accept

countingby bytes of data(not segments)

Internetchecksum

(as in UDP)


TCP seq rsquos and ACKsSeq rsquos

byte stream ldquonumberrdquo of first byte in segmentrsquos data

ACKsseq of next byte expected from other sidecumulative ACK

Q how receiver handles out-of-order segments

A TCP spec doesnrsquot say - up to implementor

Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt

of echoedlsquoCrsquo

host ACKsreceipt oflsquoCrsquo echoes

back lsquoCrsquo

timesimple telnet scenario


TCP Round Trip Time and Timeout

Q how to set TCP timeout valuelonger than RTT

but RTT variestoo short premature timeout

unnecessary retransmissions

too long slow reaction to segment loss

Q how to estimate RTTSampleRTT measured time from segment transmission until ACK receipt

ignore retransmissionsSampleRTT will vary want estimated RTT ldquosmootherrdquo

average several recent measurements not just current SampleRTT



EstimatedRTT = (1- α)EstimatedRTT + αSampleRTT

Exponential weighted moving averageinfluence of past sample decreases exponentially fasttypical value α = 0125


Example RTT estimation



Setting the timeoutEstimatedRTT plus ldquosafety marginrdquo

large variation in EstimatedRTT -gt larger safety marginfirst estimate of how much SampleRTT deviates from EstimatedRTT

TimeoutInterval = EstimatedRTT + 4DevRTT

DevRTT = (1-β)DevRTT +β|SampleRTT-EstimatedRTT|

(typically β = 025)

Then set timeout interval


Chapter 3 outline










TCP reliable data transfer

TCP creates rdt service on top of IPrsquos unreliable servicepipelined segmentscumulative acksTCP uses single retransmission timer

retransmissions are triggered by

timeout eventsduplicate acks

initially consider simplified TCP sender

ignore duplicate acksignore flow control congestion control


TCP sender eventsdata rcvd from app

Create segment with seq seq is byte-stream number of first data byte in segmentstart timer if not already running (think of timer as for oldest unacked segment)expiration interval TimeOutInterval

timeoutretransmit segment that caused timeoutrestart timer

Ack rcvdIf acknowledges previously unacked segments

update what is known to be ackedstart timer if there are outstanding segments


TCP sender(simplified)

NextSeqNum = InitialSeqNumSendBase = InitialSeqNum

loop (forever) switch(event)

event data received from application above create TCP segment with sequence number NextSeqNum if (timer currently not running)

start timerpass segment to IP NextSeqNum = NextSeqNum + length(data)

event timer timeoutretransmit not-yet-acknowledged segment with

smallest sequence numberstart timer

event ACK received with ACK field value of y if (y gt SendBase)

SendBase = yif (there are currently not-yet-acknowledged segments)

start timer

end of loop forever

Commentbull SendBase-1 last cumulatively acked byteExamplebull SendBase-1 = 71y= 73 so the rcvrwants 73+ y gt SendBase sothat new data is acked


TCP retransmission scenariosHost A

timepremature timeout

Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100


TCP retransmission scenarios (more)Host A

loss

tim

eout

Cumulative ACK scenario

Host B

X

time

SendBase= 120


TCP ACK generation [RFC 1122 RFC 2581]

Event at Receiver

Arrival of in-order segment withexpected seq All data up toexpected seq already ACKed

Arrival of in-order segment withexpected seq One other segment has ACK pending

Arrival of out-of-order segmenthigher-than-expect seq Gap detected

Arrival of segment that partially or completely fills gap

TCP Receiver action

Delayed ACK Wait up to 500msfor next segment If no next segmentsend ACK

Immediately send single cumulative ACK ACKing both in-order segments

Immediately send duplicate ACK indicating seq of next expected byte

Immediate send ACK provided thatsegment starts at lower end of gap


Fast Retransmit

time-out period often relatively long

long delay before resending lost packet

detect lost segments via duplicate ACKs

sender often sends many segments back-to-backif segment is lost there will likely be many duplicate ACKs

if sender receives 3 ACKs for the same data it supposes that segment after ACKed data was lost

fast retransmit resend segment before timer expires


Host A

tim

eout

Host B

time

X

Figure 337 Resending a segment after triple duplicate ACK




start timer

else increment count of dup ACKs received for yif (count of dup ACKs received for y = 3)

resend segment with sequence number y

Fast retransmit algorithm

a duplicate ACK for already ACKed segment

fast retransmit


Chapter 3 outline










TCP Flow Control

receive side of TCP connection has a receive buffer

speed-matching service matching the send rate to the receiving apprsquos drain rateapp process may be

slow at reading from buffer

sender wonrsquot overflowreceiverrsquos buffer by

transmitting too muchtoo fast

flow control


TCP Flow control how it works

(suppose TCP receiver discards out-of-order segments)spare room in buffer

= RcvWindow= RcvBuffer-[LastByteRcvd -

LastByteRead]

rcvr advertises spare room by including value of RcvWindow in segmentssender limits unACKed data to RcvWindow

guarantees receive buffer doesnrsquot overflow


Chapter 3 outline










TCP Connection ManagementRecall TCP sender receiver

establish ldquoconnectionrdquo before exchanging data segmentsinitialize TCP variables

seq sbuffers flow control info (eg RcvWindow)

client connection initiatorSocket clientSocket = new Socket(hostnameport

number)

server contacted by clientSocket connectionSocket = welcomeSocketaccept()

Three way handshakeStep 1 client host sends TCP

SYN segment to serverspecifies initial seq no data

Step 2 server host receives SYN replies with SYNACK segment

server allocates buffersspecifies server initial seq

Step 3 client receives SYNACK replies with ACK segment which may contain data


TCP Connection Management (cont)

Closing a connection

client closes socketclientSocketclose()

Step 1 client end system sends TCP FIN control segment to server

Step 2 server receives FIN replies with ACK Closes connection sends FIN

client server

close

close

closed

tim

ed w

ait



Step 3 client receives FIN replies with ACK

Enters ldquotimed waitrdquo -will respond with ACK to received FINs

Step 4 server receives ACK Connection closed

Note with small modification can handle simultaneous FINs

client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline










Principles of Congestion Control

Congestioninformally ldquotoo many sources sending too much data too fast for network to handlerdquodifferent from flow controlmanifestations

lost packets (buffer overflow at routers)long delays (queueing in router buffers)

a top-10 problem


Causescosts of congestion scenario 1

two senders two receiversone router infinite buffers no retransmission

large delays when congestedmaximum achievable throughput

unlimited shared output link buffers

Host Aλin original data

Host B

λout



one router finite buffers sender retransmission of timed-out packet

application-layer input = application-layer output λin = λout

transport-layer input includes retransmissions λin λin

finite shared output link buffers

Host A

λin original data

Host B

λoutλin original data plusretransmitted data

lsquo


Congestion scenario 2a ideal case

sender sends only when router buffers available


Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space

packets may get dropped at router due to full buffers

sometimes lostsender only resends if packet known to be lost (admittedly idealized)

Congestion scenario 2b known loss



Host A

λin original data

Host B


free buffer space


sometimes not lostsender only resends if packet known to be lost (admittedly idealized)

R2

R2λin

λ out

when sending at R2 some packets are retransmissions but asymptotic goodput is still R2 (why)


packets may get dropped at router due to full bufferssender times out prematurely sending two copies both of which are delivered

Host A

λin

Host B

λoutλincopy

free buffer space

Congestion scenario 2c duplicates

timeout

R2

R2λin

λ out

when sending at R2 some packets are retransmissions including duplicated that are delivered



Congestion scenario 2c duplicatesR2

λ out


ldquocostsrdquo of congestionmore work (retrans) for given ldquogoodputrdquounneeded retransmissions link carries multiple copies of pkt

decreasing goodput

R2λin


Causescosts of congestion scenario 3four sendersmultihop pathstimeoutretransmit

λin

Q what happens as and increase λ

in



Host B

λout

λin original data plus retransmitted data



another ldquocostrdquo of congestionwhen packet dropped any ldquoupstream transmission capacity used for that packet was wasted

Host A

Host B

λout


Approaches towards congestion control

end-end congestion controlno explicit feedback from networkcongestion inferred from end-system observed loss delayapproach taken by TCP

network-assisted congestion controlrouters provide feedback to end systems

single bit indicating congestion (SNA DECbit TCPIP ECN ATM)explicit rate sender should send at

Two broad approaches towards congestion control


Case study ATM ABR congestion control

ABR available bit rateldquoelastic servicerdquo if senderrsquos path ldquounderloadedrdquo

sender should use available bandwidth

if senderrsquos path congested

sender throttled to minimum guaranteed rate

RM (resource management) cellssent by sender interspersed with data cellsbits in RM cell set by switches (ldquonetwork-assistedrdquo)

NI bit no increase in rate (mild congestion)CI bit congestion indication

RM cells returned to sender by receiver with bits intact



two-byte ER (explicit rate) field in RM cellcongested switch may lower ER value in cellsenderrsquo send rate thus maximum supportable rate on path

EFCI bit in data cells set to 1 in congested switchif data cell preceding RM cell has EFCI set sender sets CI bit in returned RM cell


Chapter 3 outline










TCP congestion control additive increase multiplicative decrease

8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow

approach increase transmission rate (window size) probing for usable bandwidth until loss occurs

additive increase increase cwnd by 1 MSS every RTT until loss detectedmultiplicative decrease cut cwnd in half after loss

time

cwnd

con

gest

ion

win

dow

siz

e

saw toothbehavior probing

for bandwidth


TCP Congestion Control details

sender limits transmissionLastByteSent-LastByteAcked

le cwnd

roughly

cwnd is dynamic function of perceived network congestion

How does sender perceive congestionloss event = timeout or3 duplicate acksTCP sender reduces rate (cwnd) after loss event

three mechanismsAIMDslow startconservative after timeout events

rate = cwndRTT Bytessec


TCP Slow Start

when connection begins increase rate exponentially until first loss event

initially cwnd = 1 MSSdouble cwnd every RTTdone by incrementing cwnd for every ACK received

summary initial rate is slow but ramps up exponentially fast

Host A

RTT

Host B

time


Refinement inferring lossafter 3 dup ACKs

cwnd is cut in halfwindow then grows linearly

but after timeout eventcwnd instead set to 1 MSS window then grows exponentiallyto a threshold then grows linearly

3 dup ACKs indicates network capable of delivering some segments

timeout indicates a ldquomore alarmingrdquo congestion scenario

Philosophy


RefinementQ when should the

exponential increase switch to linear

A when cwnd gets to 12 of its value before timeout

Implementationvariable ssthreshon loss event ssthresh is set to 12 of cwnd just before loss event


Summary TCP Congestion Control

timeoutssthresh = cwnd2

cwnd = 1 MSSdupACKcount = 0

retransmit missing segment

Λcwnd gt ssthresh

congestionavoidance

cwnd = cwnd + MSS (MSScwnd)dupACKcount = 0

transmit new segment(s) as allowed

new ACK

dupACKcount++duplicate ACK

fastrecovery

cwnd = cwnd + MSStransmit new segment(s) as allowed

duplicate ACK

ssthresh= cwnd2cwnd = ssthresh + 3


dupACKcount == 3

timeoutssthresh = cwnd2cwnd = 1 dupACKcount = 0retransmit missing segment

ssthresh= cwnd2cwnd = ssthresh + 3retransmit missing segment

dupACKcount == 3cwnd = ssthreshdupACKcount = 0

New ACK

slow start




cwnd = cwnd+MSSdupACKcount = 0transmit new segment(s) as allowed

new ACKdupACKcount++duplicate ACK

Λcwnd = 1 MSS

ssthresh = 64 KBdupACKcount = 0

NewACK

NewACK

NewACK


TCP throughput

whatrsquos the average throughout of TCP as a function of window size and RTT

ignore slow startlet W be the window size when loss occurs

when window is W throughput is WRTTjust after loss window drops to W2 throughput to W2RTT average throughout 75 WRTT


TCP Futures TCP over ldquolong fat pipesrdquo

example 1500 byte segments 100ms RTT want 10 Gbps throughputrequires window size W = 83333 in-flight segmentsthroughput in terms of loss rate

L = 210-10 Wow ndash a very small loss ratenew versions of TCP for high-speed

LRTTMSSsdot221


fairness goal if K TCP sessions share same bottleneck link of bandwidth R each should have average rate of RK

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness


Why is TCP fairtwo competing sessions

additive increase gives slope of 1 as throughout increasesmultiplicative decrease decreases throughput proportionally

R

R

equal bandwidth share

Connection 1 throughput

congestion avoidance additive increaseloss decrease window by factor of 2



Fairness (more)Fairness and UDP

multimedia apps often do not use TCP

do not want rate throttled by congestion control

instead use UDPpump audiovideo at constant rate tolerate packet loss

Fairness and parallel TCP connectionsnothing prevents app from opening parallel connections between 2 hostsweb browsers do this example link of rate R supporting 9 connections

new app asks for 1 TCP gets rate R10new app asks for 11 TCPs gets R2


Chapter 3 Summaryprinciples behind transport layer services

multiplexing demultiplexingreliable data transferflow controlcongestion control

instantiation and implementation in the Internet

UDPTCP

Nextleaving the network ldquoedgerdquo (application transport layers)into the network ldquocorerdquo

Slide Number 1

Chapter 3 Transport Layer

Chapter 3 outline

Transport services and protocols



Chapter 3 outline


How demultiplexing works


Connectionless demux (cont)




Chapter 3 outline


UDP more

UDP checksum

Internet Checksum Example

Chapter 3 outline

Principles of Reliable data transfer






Rdt20 channel with bit errors








rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat


Selective repeat dilemma

Chapter 3 outline



TCP seq rsquos and ACKs





Chapter 3 outline


TCP sender events


TCP retransmission scenarios

TCP retransmission scenarios (more)


Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline

TCP Connection Management




Chapter 3 outline














Chapter 3 outline



TCP Slow Start

Refinement inferring loss

Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-2

Chapter 3 Transport LayerOur goals

understand principles behind transport layer services

multiplexingdemultiplexingreliable data transferflow controlcongestion control

learn about transport layer protocols in the Internet

UDP connectionless transportTCP connection-oriented transportTCP congestion control

Transport Layer 3-3

Chapter 3 outline









Transport Layer 3-4







Transport Layer 3-5






Transport Layer 3-6















Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-3

Chapter 3 outline









Transport Layer 3-4







Transport Layer 3-5






Transport Layer 3-6















Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-4







Transport Layer 3-5






Transport Layer 3-6















Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-5






Transport Layer 3-6















Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-6















Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-7

Chapter 3 outline









Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-8


application

transport

network

link

physical

P1 application

transport

network

link

physical

application

transport

network

link

physical

P2P3 P4P1


= process= socket




Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

Transport Layer 3-9





32 bits

applicationdata

(message)

other header fields














ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary













ClientIPB

P2

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428













ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary












ClientIPB

P1

clientIP A

P1P2P4

serverIP C

SP 9157DP 80

SP 9157DP 80

P5 P6 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



clientIPB

P1

clientIP A

P1P2

serverIP C

SP 9157DP 80

SP 9157DP 80

P4 P3

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline
















UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary








UDP more







32 bits

Applicationdata

(message)

UDP segment format



header


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


UDP checksum







1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 01 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1

1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 01 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound

sumchecksum

Presenter
Presentation Notes


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline




















sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary












sendside

receiveside











state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





state1

state2




eventactions






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






udt_send(packet)


Wait for call from

below

rdt_rcv(packet)

sender receiver



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



















udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

belowsender


Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary








udt_send(sndpkt)


udt_send(NAK)


Wait for ACK or

NAK

Wait for call from

below

rdt_send(data)

Λ






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






stop and wait




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




above


rdt_send(data)




rdt_send(data)


udt_send(sndpkt)



Wait forcall 1 from

above


ΛΛ


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


















rdt21 discussion













above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary








above


rdt_send(data)

udt_send(sndpkt)


isACK(rcvpkt1) )


Wait for ACK

0sender FSM

fragment





has_seq1(rcvpkt))


fragment

Λ










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary










rdt_send(data)

Wait for

ACK0



above


rdt_send(data)






timeout


timeout

rdt_rcv(rcvpkt)

Wait for call 0from

above

Wait for

ACK1

Λrdt_rcv(rcvpkt)

ΛΛ

Λ


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


rdt30 in action


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


rdt30 in action





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





U sender =

00830008

= 000027 L R RTT + L R

=



9 ===RLdtrans




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




sender receiver

RTT




U sender =

008 30008

= 000027 L R RTT + L R

=








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary








sender receiver

RTT





U sender =

02430008

= 00008 3 L R RTT + L R

=



Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Pipelined Protocols








Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Go-Back-NSender







timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




timeout

rdt_send(data)







base=1nextseqnum=1


Λ






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






Wait





Λ


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


GBN inaction


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Selective Repeat









Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




Selective repeat








ACK(n)otherwise

ignore

receiver









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary









Chapter 3 outline



















socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary











socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment






32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




32 bits

applicationdata

(variable length)



FSRPAUheadlen

notused



ACK ACK valid



commands)



Internetchecksum

(as in UDP)







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







Host A Host B

Usertypes

lsquoCrsquo

host ACKsreceipt



back lsquoCrsquo


























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

























Chapter 3 outline
































start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary
























start timer

end of loop forever





Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




Host B

Seq=

92 t

imeo

ut

Host A

loss

tim

eout

lost ACK scenario

Host B

X

time

Seq=

92 t

imeo

utSendBase

= 100

SendBase= 120

SendBase= 120

SendBase= 100



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



loss

tim

eout


Host B

X

time

SendBase= 120



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



Event at Receiver





TCP Receiver action






Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Fast Retransmit








Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Host A

tim

eout

Host B

time

X





start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




start timer





fast retransmit


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline










TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


TCP Flow Control






flow control





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





LastByteRead]




Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline














number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary






number)













client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







client server

close

close

closed

tim

ed w

ait







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







client server

closing

closing

closed

tim

ed w

ait

closed



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



TCP clientlifecycle

TCP serverlifecycle


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Chapter 3 outline













a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





a top-10 problem







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







Host B

λout







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







Host A

λin original data

Host B


lsquo





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





Host A

λin original data

Host B


copy

R2

R2λin

λ out

free buffer space


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


Host A

λin original data

Host B


copy

no buffer space






Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



Host A

λin original data

Host B


free buffer space



R2

R2λin

λ out




Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



Host A

λin

Host B

λoutλincopy

free buffer space


timeout

R2

R2λin

λ out





λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




λ out



decreasing goodput

R2λin



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



λin


in



Host B

λout





Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




Host A

Host B

λout





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





















Chapter 3 outline











8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



8 Kbytes

16 Kbytes

24 Kbytes

time

congestionwindow



time

cwnd

con

gest

ion

win

dow

siz

e


for bandwidth




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




le cwnd

roughly






TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


TCP Slow Start




Host A

RTT

Host B

time







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary







Philosophy











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary











Λcwnd gt ssthresh

congestionavoidance



new ACK


fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






Λcwnd = 1 MSS


NewACK

NewACK

NewACK


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary


TCP throughput








LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary





LRTTMSSsdot221



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary



TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

TCP Fairness




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary




R

R
















UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary












UDPTCP


Slide Number 1


Chapter 3 outline




Chapter 3 outline








Chapter 3 outline


UDP more

UDP checksum


Chapter 3 outline















rdt21 discussion




rdt30 sender

rdt30 in action

rdt30 in action



Pipelined protocols


Pipelined Protocols

Go-Back-N



GBN inaction

Selective Repeat


Selective repeat



Chapter 3 outline








Chapter 3 outline


TCP sender events





Fast Retransmit

Slide Number 72


Chapter 3 outline

TCP Flow Control


Chapter 3 outline





Chapter 3 outline














Chapter 3 outline



TCP Slow Start


Refinement


TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)

Chapter 3 Summary

chapter 3 transport layer - simon fraser university€¦ · transport layer. 3-1. chapter 3...

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