Chapter 5 Link Layer and LANs - Utah ECEece6962-003/chen-slides/Chapter5_1...5: DataLink Layer 5-5...

5 DataLink Layer 5-1

Chapter 5Link Layer and LANs

Computer Networking A Top Down Approach Featuring the Internet 3rd edition Jim Kurose Keith RossAddison-Wesley July 2004


Chapter 5 The Data Link LayerOur goals

understand principles behind data link layer services

error detection correctionsharing a broadcast channel multiple accesslink layer addressingreliable data transfer flow control done

instantiation and implementation of various link layer technologies


Link Layer

51 Introduction and services52 Error detection and correction 53Multiple access protocols54 Link-Layer Addressing55 Ethernet

56 Hubs and switches


Link Layer IntroductionSome terminology

hosts and routers are nodescommunication channels that connect adjacent nodes along communication path are links

wired linkswireless linksLANs

layer-2 packet is a frameencapsulates datagram

ldquolinkrdquo

data-link layer has responsibility of transferring datagram from one node to adjacent node over a link


Link layer contextDatagram transferred by different link protocols over different links

eg Ethernet on first link frame relay on intermediate links 80211 on last link

Each link protocol provides different services

eg may or may not provide rdt over link

transportation analogytrip from Princeton to Lausanne

limo Princeton to JFKplane JFK to Genevatrain Geneva to Lausanne

tourist = datagramtransport segment = communication linktransportation mode = link layer protocoltravel agent = routing algorithm


Link Layer ServicesFraming link access

encapsulate datagram into frame adding header trailerchannel access if shared mediumldquoMACrdquo addresses used in frame headers to identify source dest

bull different from IP addressReliable delivery between adjacent nodes

we learned how to do this already (chapter 3)seldom used on low bit error link (fiber some twisted pair)wireless links high error rates

bull Q why both link-level and end-end reliability


Link Layer Services (more)

Flow Controlpacing between adjacent sending and receiving nodes

Error Detectionerrors caused by signal attenuation noise receiver detects presence of errors

bull signals sender for retransmission or drops frame

Error Correctionreceiver identifies and corrects bit error(s) without resorting to retransmission

Half-duplex and full-duplexwith half duplex nodes at both ends of link can transmit but not at same time


Adaptors Communicating

link layer implemented in ldquoadaptorrdquo (aka NIC)

Ethernet card PCMCI card 80211 card

sending sideencapsulates datagram in a frameadds error checking bits rdt flow control etc

receiving sidelooks for errors rdt flow control etcextracts datagram passes to rcving node

adapter is semi-autonomouslink amp physical layers

sendingnode

frame

rcvingnode

datagram

frame

adapter adapter

link layer protocol


Link Layer

51 Introduction and services52 Error detection and correction53Multiple access protocols54 Link-Layer Addressing55 Ethernet

56 Hubs and switches57 PPP58 Link Virtualization ATM


Error DetectionEDC= Error Detection and Correction bits (redundancy)D = Data protected by error checking may include header fields

bull Error detection not 100 reliablebull protocol may miss some errors but rarelybull larger EDC field yields better detection and correction


Parity CheckingSingle Bit ParityDetect single bit errors

Two Dimensional Bit ParityDetect and correct single bit errors

0 0


Internet 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 nonethelessMore later hellip

Goal detect ldquoerrorsrdquo (eg flipped bits) in transmitted segment (note used at transport layer only)


Checksumming Cyclic Redundancy Checkview data bits D as a binary numberchoose r+1 bit pattern (generator) Ggoal choose r CRC bits R such that

ltDRgt exactly divisible by G (modulo 2) receiver knows G divides ltDRgt by G If non-zero remainder error detectedcan detect all burst errors less than r+1 bits

widely used in practice (ATM HDLC)


CRC ExampleWant

D2r XOR R = nGequivalently

D2r = nG XOR R equivalently

if we divide D2r by G want remainder R

R = remainder[ ]D2r

G


Link Layer




Multiple Access Links and ProtocolsTwo types of ldquolinksrdquo

point-to-pointPPP for dial-up accesspoint-to-point link between Ethernet switch and host

broadcast (shared wire or medium)Old-fashioned Ethernetupstream HFC80211 wireless LAN


Multiple Access protocolssingle shared broadcast channel two or more simultaneous transmissions by nodes interference

collision if node receives two or more signals at the same timemultiple access protocol

distributed algorithm that determines how nodes share channel ie determine when node can transmitcommunication about channel sharing must use channel itself

no out-of-band channel for coordination


Ideal Multiple Access Protocol

Broadcast channel of rate R bps1 When only one node wants to transmit it can send

at rate R2 When M nodes want to transmit each can send at

average rate RM3 Fully decentralized

no special node to coordinate transmissionsno synchronization of clocks slots

4 Simple


MAC Protocols a taxonomyThree broad classes

Channel Partitioningdivide channel into smaller ldquopiecesrdquo (time slots frequency code)allocate piece to node for exclusive use

Random Accesschannel not divided allow collisionsldquorecoverrdquo from collisions

ldquoTaking turnsrdquoNodes take turns but nodes with more to send can take longer turns


Channel Partitioning MAC protocols TDMA

TDMA time division multiple accessaccess to channel in rounds each station gets fixed length slot (length = pkt trans time) in each round unused slots go idle example 6-station LAN 134 have pkt slots 256 idle


Channel Partitioning MAC protocols FDMA

FDMA frequency division multiple accesschannel spectrum divided into frequency bandseach station assigned fixed frequency bandunused transmission time in frequency bands go idle example 6-station LAN 134 have pkt frequency bands 256 idle

freq

uenc

y ba

nds

time


Random Access Protocols

When node has packet to sendtransmit at full channel data rate Rno a priori coordination among nodes

two or more transmitting nodes ldquocollisionrdquorandom access MAC protocol specifies

how to detect collisionshow to recover from collisions (eg via delayed retransmissions)

Examples of random access MAC protocolsslotted ALOHAALOHACSMA CSMACD CSMACA


Slotted ALOHA

Assumptionsall frames same sizetime is divided into equal size slots time to transmit 1 framenodes start to transmit frames only at beginning of slotsnodes are synchronizedif 2 or more nodes transmit in slot all nodes detect collision

Operationwhen node obtains fresh frame it transmits in next slotno collision node can send new frame in next slotif collision node retransmits frame in each subsequent slot with prob p until success


Slotted ALOHA

Prossingle active node can continuously transmit at full rate of channelhighly decentralized only slots in nodes need to be in syncsimple

Conscollisions wasting slotsidle slotsnodes may be able to detect collision in less than time to transmit packetclock synchronization


Slotted Aloha efficiency

Suppose N nodes with many frames to send each transmits in slot with probability pprob that node 1 has success in a slot= p(1-p)N-1

prob that any node has a success = Np(1-p)N-1

For max efficiency with N nodes find p that maximizes Np(1-p)N-1

For many nodes take limit of Np(1-p)N-1 as N goes to infinity gives 1e = 37

Efficiency is the long-run fraction of successful slots when there are many nodes each with many frames to send

At best channelused for useful transmissions 37of time


Pure (unslotted) ALOHAunslotted Aloha simpler no synchronizationwhen frame first arrives

transmit immediately collision probability increases

frame sent at t0 collides with other frames sent in [t0-1t0+1]


Pure Aloha efficiencyP(success by given node) = P(node transmits)

P(no other node transmits in [t0-1t0] P(no other node transmits in [t0t0+1]

= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)

hellip choosing optimum p and then letting n -gt infty

= 1(2e) = 18 Even worse


CSMA (Carrier Sense Multiple Access)

CSMA listen before transmitIf channel sensed idle transmit entire frame

If channel sensed busy defer transmission

Human analogy donrsquot interrupt others


CSMA collisionscollisions can still occurpropagation delay means two nodes may not heareach otherrsquos transmission

collisionentire packet transmission time wasted

spatial layout of nodes

noterole of distance amp propagation delay in determining collision probability


CSMACD (Collision Detection)CSMACD carrier sensing deferral as in CSMA

collisions detected within short timecolliding transmissions aborted reducing channel wastage

collision detectioneasy in wired LANs measure signal strengths compare transmitted received signalsdifficult in wireless LANs receiver shut off while transmitting

human analogy the polite conversationalist


CSMACD collision detection


ldquoTaking Turnsrdquo MAC protocols

channel partitioning MAC protocolsshare channel efficiently and fairly at high loadinefficient at low load delay in channel access 1N bandwidth allocated even if only 1 active node

Random access MAC protocolsefficient at low load single node can fully utilize channelhigh load collision overhead

ldquotaking turnsrdquo protocolslook for best of both worlds


ldquoTaking Turnsrdquo MAC protocolsPolling

master node ldquoinvitesrdquo slave nodes to transmit in turnconcerns

polling overhead latencysingle point of failure (master)

Token passingcontrol token passed from one node to next sequentiallytoken messageconcerns

token overhead latencysingle point of failure (token)


Summary of MAC protocols

What do you do with a shared mediaChannel Partitioning by time frequency or code

bull Time Division Frequency DivisionRandom partitioning (dynamic)

bull ALOHA S-ALOHA CSMA CSMACDbull carrier sensing easy in some technologies (wire) hard

in others (wireless)bull CSMACD used in Ethernetbull CSMACA used in 80211

Taking Turnsbull polling from a central site token passing


LAN technologiesData link layer so far

services error detectioncorrection multiple access

Next LAN technologiesaddressingEthernethubs switchesPPP


Link Layer




MAC Addresses and ARP

32-bit IP address network-layer addressused to get datagram to destination IP subnet

MAC (or LAN or physical or Ethernet) address

used to get frame from one interface to another physically-connected interface (same network)48 bit MAC address (for most LANs) burned in the adapter ROM


LAN Addresses and ARPEach adapter on LAN has unique LAN address

Broadcast address =FF-FF-FF-FF-FF-FF

= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN(wired orwireless)


LAN Address (more)

MAC address allocation administered by IEEEmanufacturer buys portion of MAC address space (to assure uniqueness)Analogy

(a) MAC address like Social Security Number(b) IP address like postal address

MAC flat address portability can move LAN card from one LAN to another

IP hierarchical address NOT portabledepends on IP subnet to which node is attached


ARP Address Resolution Protocol

Each IP node (Host Router) on LAN has ARP tableARP Table IPMAC address mappings for same LAN nodes

lt IP address MAC address TTLgtTTL (Time To Live) time after which address mapping will be forgotten (typically 20 min)

Question how to determineMAC address of Bknowing Brsquos IP address

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788


ARP protocol Same LAN (network)

A wants to send datagram to B and Brsquos MAC address not in Arsquos ARP tableA broadcasts ARP query packet containing Bs IP address

Dest MAC address = FF-FF-FF-FF-FF-FFall machines on LAN receive ARP query

B receives ARP packet replies to A with its (Bs) MAC address

frame sent to Arsquos MAC address (unicast)

A caches (saves) IP-to-MAC address pair in its ARP table until information becomes old (times out)

soft state information that times out (goes away) unless refreshed

ARP is ldquoplug-and-playrdquonodes create their ARP tables without intervention from net administrator


Routing to another LANwalkthrough send datagram from A to B via R

assume A knows Brsquos IP address

Two ARP tables in router R one for each IP network (LAN)

A

RB


A creates datagram with source A destination B A uses ARP to get Rrsquos MAC address for 111111111110A creates link-layer frame with Rs MAC address as dest frame contains A-to-B IP datagramArsquos adapter sends frame Rrsquos adapter receives frame R removes IP datagram from Ethernet frame sees its destined to BR uses ARP to get Brsquos MAC address R creates frame containing A-to-B IP datagram sends to B

A

RB


DHCP Dynamic Host Configuration Protocol

Goal allow host to dynamically obtain its IP address from network server when it joins networkCan renew its lease on address in useAllows reuse of addresses (only hold address while connected

an ldquoonrdquoSupport for mobile users who want to join network (more

shortly)DHCP overview

host broadcasts ldquoDHCP discoverrdquo msgDHCP server responds with ldquoDHCP offerrdquo msghost requests IP address ldquoDHCP requestrdquo msgDHCP server sends address ldquoDHCP ackrdquo msg


DHCP client-server scenario

223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server

arriving DHCP client needsaddress in thisnetwork


DHCP client-server scenarioDHCP server 223125 arriving

client

time

DHCP discover

src 0000 68 dest 25525525525567yiaddr 0000transaction ID 654

DHCP offersrc 223125 67 dest 255255255255 68yiaddrr 223124transaction ID 654Lifetime 3600 secs

DHCP request

src 0000 68 dest 255255255255 67yiaddrr 223124transaction ID 655Lifetime 3600 secs

DHCP ACKsrc 223125 67 dest 255255255255 68yiaddrr 223124transaction ID 655Lifetime 3600 secs


Link Layer




Ethernetldquodominantrdquo wired LAN technology

cheap $20 for 100Mbsfirst widely used LAN technologySimpler cheaper than token LANs and ATMKept up with speed race 10 Mbps ndash 10 Gbps

Metcalfersquos Ethernetsketch


Star topologyBus topology popular through mid 90sNow star topology prevailsConnection choices hub or switch (more later)

hub orswitch


Ethernet Frame StructureSending adapter encapsulates IP datagram (or other

network layer protocol packet) in Ethernet frame

Preamble7 bytes with pattern 10101010 followed by one byte with pattern 10101011used to synchronize receiver sender clock rates


Ethernet Frame Structure (more)Addresses 6 bytes dest address and 6 bytes source address

if adapter receives frame with matching destination address or with broadcast address (eg ARP packet) it passes data in frame to net-layer protocolotherwise adapter discards frame

Type 2 bytes indicates the higher layer protocol (mostly IP but others may be supported such as Novell IPX and AppleTalk)CRC 4 btyes checked at receiver if error is detected the frame is simply dropped


Ethernet Frame Structure (more)

Data 46 to 1500 bytesMinimum frame size 8 preamble + 6 dest Add + 6 source add + 2 type + 46 data + 4 CRC= 72 bytes 64 bytes (512 bits) excluding 8 bytes preambleMaximum frame size 1500 data + 26 =1526 bytes


Unreliable connectionless service

Connectionless No handshaking between sending and receiving adapter Unreliable receiving adapter doesnrsquot send acks or nacks to sending adapter

stream of datagrams passed to network layer can have gapsgaps will be filled if app is using TCPotherwise app will see the gaps


Ethernet uses CSMACD

No slotsadapter doesnrsquot transmit if it senses that some other adapter is transmitting that is carrier sensetransmitting adapter aborts when it senses that another adapter is transmitting that is collision detection

Before attempting a retransmission adapter waits a random time that is random access


Ethernet CSMACD algorithm1 Adaptor receives datagram

from net layer amp creates frame

2 If adapter senses channel idle for 96 bit times it starts to transmit frame If it senses channel busy waits until channel idle for 96 bit times and then transmits

3 If adapter transmits entire frame without detecting another transmission the adapter is done with frame

4 If adapter detects another transmission while transmitting aborts and sends 48-bit jam signal

5 After aborting adapter enters exponential backoff after the n-thcollision adapter chooses a K at random from 012hellip2m-1 where m=min(n10) Adapter waits K512 bit times and returns to Step 2


Ethernetrsquos CSMACD (more)Jam Signal make sure all

other transmitters are aware of collision 48 bits

Bit time 1 microsec for 10 Mbps Ethernet for K=1023 wait time is about 50 msec

Exponential BackoffGoal adapt retransmission attempts to estimated current load

heavy load random wait will be longer

first collision choose K from 01 delay is K 512 bit transmission timesafter second collision choose K from 0123hellipafter ten collisions choose K from 01234hellip1023

Seeinteract with Javaapplet on AWL Web sitehighly recommended


CSMACD efficiency

Tprop = max prop between 2 nodes in LANttrans = time to transmit max-size frame

Efficiency goes to 1 as tprop goes to 0Goes to 1 as ttrans goes to infinityMuch better than ALOHA but still decentralized simple and cheap

transprop tt 511efficiency

+=


Propagation delay amp frame size

Propagation delay tprop

A

Suppose A sends a packet at time 0And B sees an idle channel just before t= tpropso B happily starts transmitting a frame

B detects a collision but A doesnrsquot see collision till t=2 tprop

A needs to wait for time 2 tprop to detect collisionSo A should keep transmitting during this periodhellip and keep an eye out for a possible collision


Propagation delay amp frame sizePropagation delay determines min frame size

to prevent undetected collisionsTrans time of minimum frame gt 2 tpropModern 10Mb Ethernet

Minimum frame size calculationbull 500m maximum segment lengthbull Can add repeaters up to a maximum 5 segments

(2500m)bull c in cable = 60 c in vacuum = 18 x 10^8 msbull ~ 125us one-way delaybull Add repeater and transceiver delaybull To be safe IEEE specifies a 512 ldquobit-timerdquo slot for

Ethernet = 512us bull 512 bits = 64 bytes (data payload = 46 bytes)


10BaseT and 100BaseT10100 Mbps rate latter called ldquofast ethernetrdquoT stands for Twisted PairNodes connect to a hub ldquostar topologyrdquo 100 m max distance between nodes and hub

twisted pair

hub


HubsHubs are essentially physical-layer repeaters

bits coming from one link go out all other linksat the same rateno frame bufferingno CSMACD at hub adapters detect collisionsprovides net management functionality

twisted pair

hub


Manchester encoding

Used in 10BaseTEach bit has a transitionAllows clocks in sending and receiving nodes to synchronize to each other

no need for a centralized global clock among nodesHey this is physical-layer stuff


Gbit Ethernet

uses standard Ethernet frame formatallows for point-to-point links and shared broadcast channelsin shared mode CSMACD is used short distances between nodes required for efficiencyuses hubs called here ldquoBuffered DistributorsrdquoFull-Duplex at 1 Gbps for point-to-point links10 Gbps now


Link Layer


56 Interconnections Hubs and switches57 PPP58 Link Virtualization ATM


Interconnecting with hubsBackbone hub interconnects LAN segmentsExtends max distance between nodesBut individual segment collision domains become one large collision domainCanrsquot interconnect 10BaseT amp 100BaseT

hub hub hub

hub


SwitchLink layer device

stores and forwards Ethernet framesexamines frame header and selectivelyforwards frame based on MAC dest addresswhen frame is to be forwarded on segment uses CSMACD to access segment

transparenthosts are unaware of presence of switches

plug-and-play self-learningswitches do not need to be configured


Forwarding

bull How do determine onto which LAN segment to forward framebull Looks like a routing problem

hub hubhub

switch1

2 3


Self learning

A switch has a switch tableentry in switch table

(MAC Address Interface Time Stamp)stale entries in table dropped (TTL can be 60 min)

switch learns which hosts can be reached through which interfaces

when frame received switch ldquolearnsrdquo location of sender incoming LAN segmentrecords senderlocation pair in switch table


FilteringForwardingWhen switch receives a frame

index switch table using MAC dest addressif entry found for destination

thenif dest on segment from which frame arrived

then drop the frameelse forward the frame on interface indicated

else flood

forward on all but the interface on which the frame arrived


Switch exampleSuppose C sends frame to D

Switch receives frame from from Centry in switch table that C is on interface 1because D is not in table switch forwards frame into interfaces 2 and 3

frame received by D

hub hub hub

switch

A

B CD

EF G H

I

address interfaceABEG

1123

12 3


Switch exampleSuppose D replies back with frame to C

Switch receives frame from from DEntry in switch table says that D is on interface 2because C is in table switch forwards frame only to interface 1

frame received by C

hub hub hub

switch

A

B CD

EF G H

I

address interfaceABEGC

11231


Switch traffic isolationswitch installation breaks subnet into LAN segmentsswitch filters packets

same-LAN-segment frames not usually forwarded onto other LAN segmentssegments become separate collision domains

hub hub hub

switch

collision domain collision domain

collision domain


Switches dedicated accessSwitch with many interfacesHosts have direct connection to switchNo collisions full duplex

Switching A-to-Arsquo and B-to-Brsquosimultaneously no collisions

switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches

cut-through switching frame forwarded from input to output port without first collecting entire frame

slight reduction in latencycombinations of shareddedicated 101001000 Mbps interfaces


Institutional network

hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server


Switches vs Routersboth store-and-forward devices

routers network layer devices (examine network layer headers)switches are link layer devices

routers maintain routing tables implement routing algorithmsswitches maintain switch tables implement filtering learning algorithms


Switches vs Routers (more)switches

Pros plug-and-play relatively high packet filtering and forwarding ratesCons topology restricted to a spanning tree large switched networks require large ARP tables no protection against broadcast storms

RoutersPros No spanning tree restriction intelligent routing firewall protection against broadcast stormsCons not plug-and-play larger per-packet processing time


Summary comparison

hubs routers switches

traffic isolation

no yes yes

plug amp play yes no yes

optimal routing

no yes no

cut through

yes no yes


Chapter 5 The Data Link LayerOur goals

understand principles behind data link layer services

error detection correctionsharing a broadcast channel multiple accesslink layer addressingreliable data transfer flow control done

instantiation and implementation of various link layer technologies


Link Layer








ldquolinkrdquo






























sendingnode

frame

rcvingnode

datagram

frame

adapter adapter

link layer protocol


Link Layer









0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Link Layer








ldquolinkrdquo






























sendingnode

frame

rcvingnode

datagram

frame

adapter adapter

link layer protocol


Link Layer









0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes






ldquolinkrdquo






























sendingnode

frame

rcvingnode

datagram

frame

adapter adapter

link layer protocol


Link Layer









0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes





























sendingnode

frame

rcvingnode

datagram

frame

adapter adapter

link layer protocol


Link Layer









0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Link Layer









0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes







0 0


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Internet checksum










CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes






CRC ExampleWant




R = remainder[ ]D2r

G


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Link Layer


















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes
















4 Simple












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes












freq

uenc

y ba

nds

time








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes








Slotted ALOHA




Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Slotted ALOHA


















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes
















= p (1-p)N-1 (1-p)N-1

= p (1-p)2(N-1)











































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes









































Link Layer











= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes









= adapter

1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53



LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


LAN Address (more)










1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes






1A-2F-BB-76-09-AD

58-23-D7-FA-20-B0

0C-C4-11-6F-E3-98

71-65-F7-2B-08-53

LAN

137196723

137196778

137196714

137196788














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes














A

RB



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes



A

RB









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes









223111

223112

223113

223114 223129

223122

223121

223132223131

2231327

A

BE

DHCP server




client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes



client

time

DHCP discover



DHCP request




Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Link Layer









hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes







hub orswitch




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




































CSMACD efficiency




+=




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




A












twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes









twisted pair

hub




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




twisted pair

hub


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Manchester encoding




Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Gbit Ethernet



Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Link Layer





hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes



hub hub hub

hub







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes







Forwarding


hub hubhub

switch1

2 3


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


Self learning










else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes






else flood





frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




frame received by D

hub hub hub

switch

A

B CD

EF G H

I


1123

12 3




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




frame received by C

hub hub hub

switch

A

B CD

EF G H

I


11231




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




hub hub hub

switch


collision domain




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes




switch

A

Arsquo

B

Brsquo

C

Crsquo


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes


More on Switches





hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes



hub hubhub

switch

to externalnetwork

router

IP subnet

mail server

web server










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes










Summary comparison


traffic isolation

no yes yes


optimal routing

no yes no

cut through

yes no yes

Chapter 5 Link Layer and LANs - Utah ECEece6962-003/chen-slides/Chapter5_1...5: DataLink Layer 5-5...

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Transcript of Chapter 5 Link Layer and LANs - Utah ECEece6962-003/chen-slides/Chapter5_1...5: DataLink Layer 5-5...