OutlinesReceived

due13 March 2000

OutlinesReceived

due13 March 2000 6%

MID-TERMMID-TERM Wednesday, 1 MarchWednesday, 1 March Start studying NOW!Start studying NOW! Work 4 of 5 pagesWork 4 of 5 pages 1-2 pages of the previous midterm will be on the upcoming 1-2 pages of the previous midterm will be on the upcoming

examexam AnythingAnything in the notes and reading assignment is fair game in the notes and reading assignment is fair game Equations are providedEquations are provided

Ethernet PerformanceEthernet Performance

Heard that Ethernet Throughput = 4 Mbps?Heard that Ethernet Throughput = 4 Mbps? Take it with a grain of salt.Take it with a grain of salt.Simulations show Heavy Load throughput is Simulations show Heavy Load throughput is a lot larger.a lot larger.

Simulations also show that Average Delay to Simulations also show that Average Delay to move a packet at move a packet at head of queue head of queue is small, is small, even under heavy load conditions.even under heavy load conditions.

Token Ring PerformanceToken Ring Performance

Token Ring EfficiencyToken Ring Efficiency No Load = No Load = 1/(1 + 2*NPD + TranTK/TranPK) 1/(1 + 2*NPD + TranTK/TranPK)

Heavy Load =Heavy Load = 1/(1 + (N+1)*NPD/N + TranTK/TranPK) 1/(1 + (N+1)*NPD/N + TranTK/TranPK)

= 1/(1 + NPD) ( = 1/(1 + NPD) (under certain conditionsunder certain conditions))

Ethernet & Token Ring EfficiencyEthernet & Token Ring Efficiency

1.0

0.5

0.0

.01 .10 1.0 10.0 100 NPD

Performance IssuesPerformance Issues

Slow Speed Network? Slow Speed Network? Both Ethernet & Token Ring work well Both Ethernet & Token Ring work well

Borderline Network? Borderline Network? Token Ring offers clearly superior Token Ring offers clearly superior performance performance

High Speed Network? High Speed Network? Both stink.Both stink.

Token Ring and Ethernet MAC’s don’t scale Token Ring and Ethernet MAC’s don’t scale well to long distances or high speedswell to long distances or high speeds

ANSI FDDIANSI FDDI Covers OSI Layers 1 & 2Covers OSI Layers 1 & 2 100 Mbps Line Speed100 Mbps Line Speed Originally Dual Counter-Rotating RingsOriginally Dual Counter-Rotating Rings MAC is MAC is TimedTimed Token Ring using RAT Token Ring using RAT Data traffic can only be passed ifData traffic can only be passed if

TRT < TTRT, and then only for TRT < TTRT, and then only for TTRT-TRT secondsTTRT-TRT seconds

Has Priorities. Has Priorities. MMAT = 2*TTRTMMAT = 2*TTRT

FDDI PerformanceFDDI Performance

FDDI EfficiencyFDDI Efficiency No Load = No Load = TranPK/(1 + NPD + TranTK/TranPK) TranPK/(1 + NPD + TranTK/TranPK)

Heavy Load = Heavy Load = (TTRT - Prop - N*TranTK)/TTRT (TTRT - Prop - N*TranTK)/TTRT

FDDI StatusFDDI Status ‘‘Looked down upon’ in trade pubsLooked down upon’ in trade pubs

Still an important protocolStill an important protocol Sees more use than is commonly acknowledgedSees more use than is commonly acknowledged

Used mostly as a backbone Used mostly as a backbone Roughly 50-60% corporate networksRoughly 50-60% corporate networks Internet NAP’s & MAE’sInternet NAP’s & MAE’s Bell AtlanticBell Atlantic

New use declining - Glory days are over New use declining - Glory days are over

Hi Speed LAN’s & MAN’s (Jan 1994)Hi Speed LAN’s & MAN’s (Jan 1994)

FDDIFDDI

Hi Speed LAN’s & MAN’s (January 2000)

Hi Speed LAN’s & MAN’s (January 2000) FDDIFDDI ATMATM

100 Mbps Ethernet 100 Mbps Ethernet 100 Mbps Token Ring100 Mbps Token Ring 1 Gbps Ethernet1 Gbps Ethernet

Medium DistanceConnectivity

Short DistanceConnectivity

MultiplexingMultiplexing

Splitting a chunk of Bandwidth Splitting a chunk of Bandwidth up into channelsup into channels

Channel can carry one conversationChannel can carry one conversation

FDM, TDM, & StatMuxFDM, TDM, & StatMux

FDMFDMfrequency

tim

eDifferent channels use some of the frequency all of the time.

1 2 3 4 5

TDMTDMfrequency

tim

e

1

2

3

1

etc.

Different channels use all of the frequency some of the time.

StatMuxStatMuxfrequency

tim

e

1

3

1

2

Different channels use all of the frequency some of the time,at random, as needed.

StatMux vs. TDM & FDMStatMux vs. TDM & FDM

uses bandwidth more efficiently for uses bandwidth more efficiently for bursty trafficbursty traffic

requires more overheadrequires more overhead has more variable deliverieshas more variable deliveries requires more complex & expensive requires more complex & expensive

hardwarehardware

Switching: How Long will auser get to use a channel?

Switching: How Long will auser get to use a channel?

For the duration of the conversation?For the duration of the conversation?Circuit SwitchingCircuit Switching

For a tiny, variable length, portion of the For a tiny, variable length, portion of the conversation?conversation?

Packet SwitchingPacket Switching Circuit vs. Packet SwitchingCircuit vs. Packet Switching

Circuit has less end-to-end delayCircuit has less end-to-end delayCircuit is less complex & cheaper Circuit is less complex & cheaper Packet is more efficient for Bursty TrafficPacket is more efficient for Bursty Traffic

StatMux TDM FDM

Circuit

Packet

Cell

MULTIPLEXINGS

WIT

CH

ING

commonfor voice

commonfor data

Repeater or HubRepeater or Hub

Operates at OSI Level 1Operates at OSI Level 1 ‘‘Electric Cable’Electric Cable’

Traffic arriving at an input is Traffic arriving at an input is immediatelyimmediately copied to all outputs.copied to all outputs.