ECEN5553 Telecom Systems Week #3Read[4a] "High Speed Ethernet: A Planning Guide"[4b] "What If Ethernet Failed?"[4c] "8 Ethernet Predictions for 2014"[5a] "Is Your Ethernet Fast Enough?"[5b] "Showdown Coming on Ethernet Standard to Serve Faster

Wi-Fi"[6a] "Browse at Your Own Risk"[6b] "The Data Brokers: Selling Your Personal Information"Exam #1 Lecture 15, 21 September (Live)

No later than 28 September (Remote DL)Outline 7 October 2015, Lecture 22 (Live)

No later than 14 October (Remote DL)

ECEN5553 Telecom Systems Week #3Read[4a] "High Speed Ethernet: A Planning Guide"[4b] "What If Ethernet Failed?"[4c] "8 Ethernet Predictions for 2014"[5a] "Is Your Ethernet Fast Enough?"[5b] "Showdown Coming on Ethernet Standard to Serve Faster

Wi-Fi"[6a] "Browse at Your Own Risk"[6b] "The Data Brokers: Selling Your Personal Information"Exam #1 Lecture 15, 21 September (Live)

No later than 28 September (Remote DL)Outline 7 October 2015, Lecture 22 (Live)

No later than 14 October (Remote DL)

OutlinesReceived

due 7 October (local)14 October (remote)

OutlinesReceived

due 7 October (local)14 October (remote)

0 %

802.3 MAC Flow Chart802.3 MAC Flow Chart

Packet to Send?

No

Yes

Set Collision Couter= 0

Traffic on Network?

Yes

No

Send Packet Collision?

No

JamYes

Bump CollisionCounter by +1

16th Collision?

Drop Packet.Notify Higher Layer

Yes

Back-Off

No

Major Drawbacks of CSMA/CDMajor Drawbacks of CSMA/CD

MMAT equals infinityMMAT equals infinity(No guaranteed Bandwidth)(No guaranteed Bandwidth)

No PrioritiesNo Priorities

These make 802.3 Ethernet marginal,These make 802.3 Ethernet marginal,at best, for Multimedia Traffic.at best, for Multimedia Traffic.

802.3 Packet Format802.3 Packet Format

Pre SFD DestinationAddress

SourceAddress

Len

CRCData + Padding

Bytes: 7 1 6 6 2

46-1500 4

PreamblePreamble

time

+1

volts

0

-1

T

0 0

LogicOne

LogicZero Series of pulses

generated atreceiver T secondsapart & in middleof each symbol.

Transmitting a FileTransmitting a File Broken into smaller packetsBroken into smaller packets Initial packets from Layer 5Initial packets from Layer 5

Open Logical ConnectionOpen Logical Connection Packets from Layer 7Packets from Layer 7

“Data” Contains Layer 7 traffic“Data” Contains Layer 7 traffic“Data” Contains Layer 3-6 info“Data” Contains Layer 3-6 info

Packets from Layer 4Packets from Layer 4AcknowledgementsAcknowledgements

Final packets from Layer 5Final packets from Layer 5Close Logical ConnectionClose Logical Connection

10Base5 & 10Base2 (Obsolete)10Base5 & 10Base2 (Obsolete)

PC PC Printer

Logical & Physical BusAll nodes monitor traffic

Nodes share 10 Mbps

Coax Cable

10Base5 "Vampire Tap"10Base2 "T" connection

Images from Wikipedia

10BaseT & Shared Hub10BaseT & Shared Hub

PC

PC

PC

PC

Hub

Logical Bus & Physical StarShared hub (OSI Level 1) copies input bits to all outputs.

All nodes monitor traffic. 4 nodes share 10 Mbps.

Twisted Pair

10BaseT & Switched Hub10BaseT & Switched Hub

PC

PC

PC

PC

Switch

Logical Bus & Physical StarSwitched Hub (OSI Level 1 & 2) copies packet to proper output.

Only the destination monitors traffic. This example system can move up to 20 Mbps

provided the packet source & destinations differ.

10BaseT & Switched Hub10BaseT & Switched Hub

PC

PC

PC

PC

SwitchedHub

Logical Bus & Physical Star

Each node shares 10 Mbps with the Switched Hub.

10BaseT & Switched Hub10BaseT & Switched Hub

PC

PC

PC

PC

SwitchedHub

Using Half Duplex 10BaseT,a collision occurs if PC & Switched Hub

simultaneously transmit.

reception isscrewed up

IEEE 802.3u 100 Mbps Fast Ethernet

IEEE 802.3u 100 Mbps Fast Ethernet

Preserves CSMA/CDPreserves CSMA/CD Preserves Packet FormatPreserves Packet Format Maximum End-to-End Lengths (a.k.a. Maximum End-to-End Lengths (a.k.a.

Collision Domain) reduced to keep Collision Domain) reduced to keep Normalized Propagation Delay lowNormalized Propagation Delay low

Sales exceed 10 Mbps as of ‘98Sales exceed 10 Mbps as of ‘98

Ethernet Switch Port SalesEthernet Switch Port SalesS

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Back around 1994 to 1995…Back around 1994 to 1995… Two 100 Mbps "Ethernets" introducedTwo 100 Mbps "Ethernets" introduced Version A Version A

CSMA/CD MAC, Ethernet FramesCSMA/CD MAC, Ethernet Frames Version BVersion B

Demand Priority MAC, Ethernet FramesDemand Priority MAC, Ethernet Frames IEEE said Version A is EthernetIEEE said Version A is Ethernet

IEEE 802.3u Fast EthernetIEEE 802.3u Fast Ethernet IEEE said Version B is not EthernetIEEE said Version B is not Ethernet

IEEE 802.12 100VG-AnyLANIEEE 802.12 100VG-AnyLAN 802.12 is currently Dead802.12 is currently Dead

RIP

IEEE 802.3z1 Gbps Ethernet (1998)

IEEE 802.3z1 Gbps Ethernet (1998)

Uses an extended version of CSMA/CD, Uses an extended version of CSMA/CD, including "Frame Bursting"including "Frame Bursting"

Best performance uses full duplex connections Best performance uses full duplex connections & switched hubs& switched hubs CSMA/CD included so it can be called EthernetCSMA/CD included so it can be called Ethernet

Collision Domain same as Fast EthernetCollision Domain same as Fast Ethernet Preserves Packet FormatPreserves Packet Format Fiber or Cat6 CablesFiber or Cat6 Cables

Full Duplex SystemFull Duplex System

PC

PC

PC

PC

SwitchedHub

All > 10 Gbps, most 1 Gbps, & many 100 Mbps systems are Full Duplex.Net IC’s are designed to simultaneously transmit & receive.

Line no longer shared. No Collisions. No need for CSMA/CD.

IEEE 802.3ae 10 Gbps “Ethernet” (2002)

IEEE 802.3ae 10 Gbps “Ethernet” (2002)

Standard as of June 2002Standard as of June 2002 Does not use CSMA/CDDoes not use CSMA/CD

Uses switched hubs & full duplex Uses switched hubs & full duplex connectionsconnections

Uses Ethernet frame formatUses Ethernet frame format Initial available products used fiberInitial available products used fiber

Copper cabling now an optionCopper cabling now an option

IEEE 802.3ba 40 & 100 Gbps “Ethernet” (2010)

IEEE 802.3ba 40 & 100 Gbps “Ethernet” (2010)

Standard as of June 2010Standard as of June 2010 Does not use CSMA/CDDoes not use CSMA/CD

Uses switched hubs & full duplex connectionsUses switched hubs & full duplex connections Uses Ethernet frame formatUses Ethernet frame format

Copper cabling an option Copper cabling an option 7-10 m, 10 twisted pairs required7-10 m, 10 twisted pairs required

Mostly uses fiberMostly uses fiber

IEEE 802.1p Priority TagsIEEE 802.1p Priority Tags

8 priorities8 priorities MAC protocols remain unchangedMAC protocols remain unchanged Used by 802.1p enabled switchesUsed by 802.1p enabled switches

Allows interactive voice or video to receive Allows interactive voice or video to receive preferential treatment on an Ethernet LANpreferential treatment on an Ethernet LAN

Many Ethernet Physical Layer Standards ExistMany Ethernet Physical Layer Standards Exist

source: "Evolution of Ethernet Standards in the IEEE 802.3 Working Group", IEEE Communications Magazine, August 2013

LAN ThroughputLAN Throughput AverageAverage bit transmission rate actually available for use bit transmission rate actually available for use Throughput = Efficiency * Line SpeedThroughput = Efficiency * Line Speed Shared Half Duplex NetworkShared Half Duplex Network

No Load Efficiency: ≈ 100%No Load Efficiency: ≈ 100% Actually a little less since frames Actually a little less since frames

can't be transmitted back-to-backcan't be transmitted back-to-back Heavy Load Efficiency: ≈ 1/(1+5*NPD)Heavy Load Efficiency: ≈ 1/(1+5*NPD)

Shared network: apply to entire networkShared network: apply to entire network Switched network: apply between switched hubSwitched network: apply between switched hub

& end device& end device Switched Full Duplex Network EfficiencySwitched Full Duplex Network Efficiency

≈ ≈ 100%100%

These areEstimates.

10BaseT & Shared Hub10BaseT & Shared Hub

PC

PC

PC

PC

Hub

Logical Bus & Physical StarShared hub (OSI Level 1) copies input bits to all outputs.

All nodes monitor traffic. 4 nodes share 10 Mbps. Max end-to-end distance is 79 meters.

53 m

26 m

8 m

17 m

10BaseT & Switched Hub10BaseT & Switched Hub

PC

PC

PC

PC

Switch

Logical Bus & Physical StarSwitched hub (OSI Level 1 & 2) is packet & MAC aware.

Nodes don't see all traffic.Line shared between node & switch.

η Distance to use is PC to Hub specific.

53 m

26 m

8 m

17 m

Ethernet PerformanceEthernet Performance

Simulations show CSMA/CD is very Simulations show CSMA/CD is very efficient for slow speed Networks.efficient for slow speed Networks. Shared Ethernet efficiency equation reasonably Shared Ethernet efficiency equation reasonably

accurate.accurate. 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 usually is usually small, even under heavy load conditions.small, even under heavy load conditions.

Shared 802.3 LAN EfficienciesShared 802.3 LAN Efficiencies 500 m end-to-end500 m end-to-end

Heavy Load ConditionsHeavy Load Conditions 100 B packets: Formula = .8809 efficiency100 B packets: Formula = .8809 efficiency

5 nodes: 5 nodes: .9986 simulated.9986 simulated50 nodes:50 nodes: .6980 simulated.6980 simulated

1500 B packets: Formula = .9911 efficiency1500 B packets: Formula = .9911 efficiency5 nodes:5 nodes: .9953 simulated.9953 simulated50 nodes:50 nodes: .9532 simulated.9532 simulated

Conclusion: Conclusion: Heavy Load Heavy Load ηη reasonably accurate reasonably accurate

Head of Line PerformanceHead of Line Performance 185 m end-to-end, 130 byte packets185 m end-to-end, 130 byte packets 5 nodes5 nodes

> 90% of packets do not collide> 90% of packets do not collideAverage collisions/packet = .05Average collisions/packet = .05Average delay to transmit = 51 microsec.Average delay to transmit = 51 microsec.Maximum delay to transmit = 11.3 msec.Maximum delay to transmit = 11.3 msec.

50 nodes50 nodes> 45% collide one or more times (2% 16x)> 45% collide one or more times (2% 16x)Average collisions/packet = .93Average collisions/packet = .93Average delay to transmit = 340 microsec.Average delay to transmit = 340 microsec.Maximum delay to transmit = 236 msecMaximum delay to transmit = 236 msec

LAN HistoryIEEE 802.5 Token Ring LAN HistoryIEEE 802.5 Token Ring

Based on early 1980’s technologyBased on early 1980’s technology Covers OSI Layers 1 & 2Covers OSI Layers 1 & 2 4 or 16 Mbps Line Speed4 or 16 Mbps Line Speed Logical RingLogical Ring A ‘Token’ is passed around the ringA ‘Token’ is passed around the ring

Node must have the Token to transmitNode must have the Token to transmit Guaranteed BandwidthGuaranteed Bandwidth Has PrioritiesHas Priorities

IEEE 802.5 Token Ring IEEE 802.5 Token Ring Technically Superior to shared EthernetTechnically Superior to shared Ethernet Similar evolution to EthernetSimilar evolution to Ethernet

Logical & Physical RingLogical & Physical Ring Logical Ring, Shared Physical StarLogical Ring, Shared Physical Star Logical Ring, Switched Physical StarLogical Ring, Switched Physical Star

100 Mbps products available in ’98100 Mbps products available in ’98 3 years after Fast Ethernet3 years after Fast Ethernet

Sales have crashed. 802.5 is dead. Sales have crashed. 802.5 is dead.

RIP

Ethernet & Token Ring Shared Network EfficiencyEthernet & Token Ring Shared Network Efficiency1.0

0.5

0.0

.01 .10 1.0 10.0 100 NPD

EfficienciesToken Ring 1/(1 + NPD)Ethernet 1/(1 + 5*NPD)

Shared Network Performance IssuesShared Network Performance 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

Shared Ethernet EfficiencyDesigned to operate as "Low Speed"Shared Ethernet EfficiencyDesigned to operate as "Low Speed"

1.0

0.5

0.0

.01 .10 1.0 10.0 100 NPD

Standard CSMA/CD

Low Speed Network?This configuration...Low Speed Network?This configuration...

PC

PC

PC

Server

Hub

10BaseT & Shared Hub

... is as good as this one...... is as good as this one...

PC

PC

PC

Server

SwitchedHub

10BaseT & Switched Hub ...IF traffic mostly going to/from same machine...IF traffic mostly going to/from same machine Switched Hub better if diverse traffic flowSwitched Hub better if diverse traffic flow

This configuration is even better.This configuration is even better.

PC

PC

PC

Server

Switch

Server on a higher speed line.Server on a higher speed line.

100 Mbps 10 Mbps

10 Mbps 1 Gbps

Shared Ethernet EfficiencyGbps has higher NPDShared Ethernet EfficiencyGbps has higher NPD

1.0

0.5

0.0

.01 .10 1.0 10.0 100 NPD

101.1

High Speed Network?This configuration has

horrible throughput.

High Speed Network?This configuration has

horrible throughput.

PC

PC

PC

Server

SharedHub

1 or 10 Gbps & Shared HubUnder heavy load, too much time spent recovering from collisions.

Ethernet (Shared) HubEthernet (Shared) 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 other ports on a bit- copied to all other ports on a bit-by bit basis.by bit basis.

Used on LAN's. Pretty much obsolete.Used on LAN's. Pretty much obsolete. Repeater = single input & single output hubRepeater = single input & single output hub

Not used much on Ethernet any moreNot used much on Ethernet any more Generally now only used on WAN long haul Generally now only used on WAN long haul

May be different protocol than EthernetMay be different protocol than Ethernet

Black Box Performance...Black Box Performance...

OSI Level 1LAN Hub

Two packets simultaneously show up at input...

From Node A

Node B

Node C

To Node A

Node B

Node C

Black Box Performance...Black Box Performance...

... will overwrite each other, i.e. garbage out.

a.k.a. Shared Hub

OSI Level 1LAN Hub

From Node A

Node B

Node C

To Node A

Node B

Node C

Black Box Performance...Black Box Performance...

Two packets simultaneously show up at input...

OSI Level 1-2 (Switch)

or 1-3 (Router)

Black Box Performance...Black Box Performance...

... one will be transmitted (when allowed by MAC), the other momentarily buffered...

OSI Level 1-2 (Switch)

or 1-3 (Router)

Black Box Performance...Black Box Performance...

... and then transmitted.

OSI Level 2/3Switch

or Router

10BaseT & Shared Hub10BaseT & Shared Hub

PC

PC

PC

PC

Hub

One big collision domain.

53 m

26 m

8 m

17 m

10BaseT & Half Duplex Switch10BaseT & Half Duplex Switch

PC

PC

PC

PC

Switch

Four smaller collision domains.

53 m

26 m

8 m

17 m

ExampleExample

World

7Users

7UsersHub 1

Hub 2

If Box 1 & 2 are Level 1 HubsOne Big Collision Domain15 Nodes share 10 MbpsEach node gets average of 10/15 Mbps

10BaseT

Right Side to World gets7/15th of available BW,

on average.

ExampleExample

World

7Users

7UsersSw 1

Sw 2

If Box 1 & 2 are Level 2 SwitchesEach node shares 10 Mbps with SwitchRight Hand Side is on one 10 Mbps line.

10BaseT

Right Side to World gets_____ of available BW.

1/8th

(Was 7/15th)

Right hand side sees increased delays.Can be alleviated with100 Mbps Box 1 ↔ Box 2 link.

Switched Hubs or BridgeSwitched Hubs or Bridge On Power Up know nothingOn Power Up know nothing When a packet arrives at an input port...When a packet arrives at an input port...

Look-Up Table consultedLook-Up Table consulted Source MAC address not in table?Source MAC address not in table?

Table Updated: MAC address & Port matchedTable Updated: MAC address & Port matched

Destination MAC address not in table?Destination MAC address not in table? Packet broadcast to all outputs (a.k.a. flooding)Packet broadcast to all outputs (a.k.a. flooding)

Destination MAC address in table?Destination MAC address in table? Packet shipped to proper outputPacket shipped to proper output

Look-up Table update is dependent on packet arrivalsLook-up Table update is dependent on packet arrivals

RouterRouter Operates at OSI Layers 1, 2, & 3Operates at OSI Layers 1, 2, & 3 Capable of making complex routing decisionsCapable of making complex routing decisions

‘‘peers into’ packets and examines Layer 3 addresspeers into’ packets and examines Layer 3 address Very useful on Large Networks with multiple end-to-end Very useful on Large Networks with multiple end-to-end

pathspaths Routers frequently exchange connectivity info with Routers frequently exchange connectivity info with

neighboring Routersneighboring Routers Routing Algorithms used to update Routing Algorithms used to update

Routing (Look-Up) Tables Routing (Look-Up) Tables Tables updated independently of traffic Tables updated independently of traffic

Bridging versus RoutingBridging versus Routing Ethernet Bridge, Switch, or Switched HubEthernet Bridge, Switch, or Switched Hub

Uses Layer 2 MAC AddressUses Layer 2 MAC Address Unknown Destination? Flooded Unknown Destination? Flooded Look-up Table updates are packet dependentLook-up Table updates are packet dependent

RouterRouter Uses Layer 3 Internet Protocol Address Uses Layer 3 Internet Protocol Address Unknown Destination? Default locationUnknown Destination? Default location Look-up Tables updated independently of trafficLook-up Tables updated independently of traffic

Small Network? Doesn't matterSmall Network? Doesn't matter Big Network? Floods not a good idea.Big Network? Floods not a good idea.

Ethernet SwitchEthernet Switch

Pre SFD DestinationAddress

SourceAddress

Len

CRCData + Padding

Bytes: 7 1 6 6 2

46-1500 4

Uses MAC Source Address to populate Look-Up TableUses MAC Destination Address & Table for I/O Decision

RouterRouter

MACDestination

Address

MACSource

Address

CRCData + Padding

Bytes: 7 1 6 6 2

20 20 6-1460 4

IPv4 TCP

Populates Look-Up table independently of traffic.Uses Destination IP Address & Table for I/O Decision