chapter 3 transport layer computer networking: a top down approach 6 th edition jim kurose, keith...

Chapter 3Transport

Layer

Computer Networking A

Top Down Approach

6th edition Jim Kurose Keith Ross

Addison-WesleyMarch 2012

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 see the animations and 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) that you mention their

source (after all wersquod like people to use our book) If you post any slides 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 1996-2012 JF Kurose and KW Ross All Rights Reserved

The course notes are adapted for Bucknellrsquos CSCI 363Xiannong MengSpring 2014

Transport Layer 3-1

Transport Layer 3-2

Chapter 3 outline

31 transport-layer services32 multiplexing and demultiplexing33 connectionless transport UDP34 principles of reliable data

transfer

35 connection-oriented transport TCP segment

structure reliable data

transfer flow control connection

management36 principles of

congestion control

37 TCP congestion control

Transport Layer 3-3

congestion informally ldquotoo many sources

sending too much data too fast for network to handlerdquo

different from flow control manifestations

lost packets (buffer overflow at routers)

long delays (queueing in router buffers)

a top-10 problem

Principles of congestion control

Transport Layer 3-4

Causescosts of congestion scenario 1 two senders two

receivers one router infinite

buffers output link capacity

R no retransmission

maximum per-connection throughput R2

unlimited shared output link buffers

Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2d

ela

ylin

large delays as arrival rate lin approaches capacity

Transport Layer 3-5

one router finite buffers sender retransmission of timed-out

packet application-layer input = application-

layer output lin = lout

transport-layer input includes retransmissions lin lin

finite shared output link buffers

Host A

lin original data

Host B

loutlin original data plus

retransmitted data

lsquo

Causescosts of congestion scenario 2

Transport Layer 3-6

idealization perfect knowledge

sender sends only when router buffers available


lin original dataloutlin original data plus

retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space

Idealization known loss packets can be lost dropped at router due to full buffers

sender only resends if packet known to be lost


A

Host B

Transport Layer 3-8


retransmitted data

free buffer space

Causescosts of congestion scenario 2 Idealization

known loss packets can be lost dropped at router due to full buffers


R2

R2lin

l out

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

A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out

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

Host B

Realistic duplicates packets can be lost

dropped at router due to full buffers

sender times out prematurely sending two copies both of which are delivered


Transport Layer 3-10

R2

l out


ldquocostsrdquo of congestion more work (retrans) for given ldquogoodputrdquo unneeded retransmissions link carries multiple

copies of pkt decreasing goodput

R2lin

Causescosts of congestion scenario 2 Realistic duplicates packets can be lost




four senders multihop paths timeoutretransmit

Q what happens as lin and linrsquo increase


Host A lout


Host B

Host CHost D

lin original data

lin original data plus

retransmitted data

A as red linrsquo increases all arriving blue pkts at upper queue are dropped blue throughput g 0


another ldquocostrdquo of congestion when packet dropped any ldquoupstream

transmission capacity used for that packet was wasted


C2

C2

l ou

t

linrsquo


Approaches towards congestion controltwo broad approaches towards congestion

control

end-end congestion control

no explicit feedback from network

congestion inferred from end-system observed loss delay

approach taken by TCP

network-assisted congestion control

routers provide feedback to end systemssingle bit indicating congestion (SNA DECbit TCPIP ECN ATM)

explicit rate for sender to send at


Chapter 3 outline


transfer





congestion control



TCP congestion control additive increase multiplicative decrease

approach sender increases 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

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize

AIMD saw toothbehavior probing

for bandwidth

additively increase window size helliphellip until loss occurs (then cut window in half)

time


TCP Congestion Control details

sender limits transmission

cwnd is dynamic function of perceived network congestion

TCP sending rate roughly send

cwnd bytes wait RTT for ACKS then send more bytes

last byteACKed sent not-

yet ACKed(ldquoin-flightrdquo)

last byte sent

cwnd

LastByteSent-LastByteAcked

lt cwnd

sender sequence number space

rate ~~cwnd

RTTbytessec


TCP Slow Start when connection

begins increase rate exponentially until first loss event initially cwnd = 1

MSS double cwnd every

RTT done by

incrementing cwnd for every ACK received

summary initial rate is slow but ramps up exponentially fast

Host A

one segment

RT

T

Host B

time

two segments

four segments


TCP detecting reacting to loss

loss indicated by timeout cwnd set to 1 MSS window then grows exponentially (as in

slow start) to threshold then grows linearly

loss indicated by 3 duplicate ACKs TCP RENO dup ACKs indicate network capable of

delivering some segments cwnd is cut in half window then grows

linearly TCP Tahoe (Van Jacobson1988) always

sets cwnd to 1 (timeout or 3 duplicate acks)

Tahoe Reno and Vegas TCP Tahoe (~1988 Van Jacobson) BSD Unix

43 aka BSD Network Release 10 (BNR1) additive increase and multiplicative decrease slow start no fast retransmission

TCP Reno (~1990) BNR2 BNR1 plus fast retransmission header prediction (fast path for pure ACKs and in-order packets) delayed ACKs

TCP Vegas (~1994 Brakmo OrsquoMalley and Peterson) varying congestion window size w between a and b based on diff = (expected ndash sample) rate of transmission If diff lt a (more capacity available) increase w by one if diff gt b (showing congestion) decrease w by one



Q when should the exponential increase switch to linear

A when cwnd gets to 12 of its value before timeout

Implementation variable ssthresh on loss event ssthresh is set to 12 of cwnd just before loss event

TCP switching from slow start to CA


Summary TCP Congestion Control

timeoutssthresh = cwnd2

cwnd = 1 MSSdupACKcount = 0

retransmit missing segment

Lcwnd 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

Lcwnd = 1 MSS

ssthresh = 64 KBdupACKcount = 0

NewACK

NewACK

NewACK


TCP throughput avg TCP thruput as function of window

size RTT ignore slow start assume always data to send

W window size (measured in bytes) where loss occurs avg window size ( in-flight bytes) is frac34 W avg thruput is 34W per RTT

W

W2

avg TCP thruput = 34WRTTbytessec


TCP Futures TCP over ldquolong fat pipesrdquo example 1500 byte segments 100ms RTT

want 10 Gbps throughput (1500 bytes = 12000 bits seg 100 ms can carry 83333 segments at 10Gbps)

requires W = 83333 in-flight segments throughput in terms of segment loss

probability L [Mathis 1997]

to achieve 10 Gbps throughput need a loss rate of L = 210-10 ndash a very small loss rate

new versions of TCP for high-speed

TCP throughput = 122 MSSRTT L


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 Fairness

TCP connection 2


Why is TCP fairtwo competing sessions additive increase gives slope of 1 as throughout

increases multiplicative decrease decreases throughput

proportionally R

R

equal bandwidth share

Connection 1 throughput

Con

nect

ion

2 th

roug

h pu t

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 UDP send

audiovideo at constant rate tolerate packet loss

Fairness parallel TCP connections

application can open multiple parallel connections between two hosts

web browsers do this

eg link of rate R with 9 existing connections new app asks for 1 TCP gets

rate R10 new app asks for 11 TCPs

gets R2

Examine some source code Linux 26 implementation of TCP

congestion control httpwwwcsfsuedu~bakerdevices

lxrhttpsourcelinuxnetipv4tcp_congc

Look for snd_cwnd tcp_slow_start tcp_cong_avoid_ai tcp_reno_cong_avoid



Chapter 3 summary principles behind

transport layer servicesmultiplexing

demultiplexing reliable data

transfer flow control congestion control

instantiation implementation in the InternetUDP TCP

next leaving the

network ldquoedgerdquo (application transport layers)

into the network ldquocorerdquo

Slide 1

Chapter 3 outline




Causescosts of congestion scenario 2 (2)







Approaches towards congestion control

Chapter 3 outline (2)

TCP congestion control additive increase multiplicative decrea


TCP Slow Start


Tahoe Reno and Vegas



TCP throughput

TCP Futures TCP over ldquolong fat pipesrdquo

TCP Fairness

Why is TCP fair

Fairness (more)

Examine some source code

Chapter 3 summary

Transport Layer 3-2

Chapter 3 outline


transfer





congestion control


Transport Layer 3-3






a top-10 problem


Transport Layer 3-4




R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2d

ela

ylin


Transport Layer 3-5






Host A

lin original data

Host B


retransmitted data

lsquo


Transport Layer 3-6





retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-3






a top-10 problem


Transport Layer 3-4




R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2d

ela

ylin


Transport Layer 3-5






Host A

lin original data

Host B


retransmitted data

lsquo


Transport Layer 3-6





retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-4




R no retransmission



Host A

original data lin

Host B

throughput lout

R2

R2

l out

lin R2d

ela

ylin


Transport Layer 3-5






Host A

lin original data

Host B


retransmitted data

lsquo


Transport Layer 3-6





retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-5






Host A

lin original data

Host B


retransmitted data

lsquo


Transport Layer 3-6





retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-6





retransmitted data

copy

free buffer space

R2

R2

l out

lin


Host B

A

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-7


retransmitted data

copy

no buffer space




A

Host B

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-8


retransmitted data

free buffer space




R2

R2lin

l out


A

Host B

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

Transport Layer 3-9

A

lin loutlincopy

free buffer space

timeout

R2

R2lin

l out


Host B






R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary


R2

l out




R2lin








Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary





Host A lout


Host B

Host CHost D

lin original data


retransmitted data






C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary





C2

C2

l ou

t

linrsquo



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary



control









Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary


Chapter 3 outline


transfer





congestion control






after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary





after loss

cwnd

TC

P s

end

er

cong

estio

n w

indo

w s

ize


for bandwidth


time









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary









last byte sent

cwnd


lt cwnd


rate ~~cwnd

RTTbytessec





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary





RTT done by



Host A

one segment

RT

T

Host B

time

two segments

four segments
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary
























Lcwnd gt ssthresh

congestionavoidance



new ACK

dupACKcount++

duplicate ACK

fastrecovery


duplicate ACK



dupACKcount == 3




New ACK

slow start






duplicate ACK

Lcwnd = 1 MSS


NewACK

NewACK

NewACK





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary





W

W2












TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary











TCP connection 1

bottleneckrouter

capacity R

TCP Fairness

TCP connection 2




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary




proportionally R

R



Con

nect

ion

2 th

roug

h pu t














gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary












gets R2












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary












next leaving the



Slide 1

Chapter 3 outline















TCP Slow Start





TCP throughput


TCP Fairness

Why is TCP fair

Fairness (more)


Chapter 3 summary

chapter 3 transport layer computer networking: a top down approach 6 th edition jim kurose, keith...

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