3rd Edition, Chapter 5 - University of Tennessee.ppt

LinkLayer5-*Chapter5:Linklayerourgoals:understandprinciplesbehindlinklayerservices:errordetection,correctionsharingabroadcastchannel:works:,VLANsinstantiation,implementationofvariouslinklayertechnologiesLinkLayer5-*Linklayer,LANs:,,,:-*Linklayer:introductionterminology:hostsandrouters:municationpath:linkswiredlinkswirelesslinksLANslayer-2packet:frame,encapsulatesdatagramdata-linklayerhasresponsibilityoftransferringdatagramfromonenodetophysicallyadjacentnodeoveralinkglobalISPLinkLayer5-*Linklayer:contextdatagramtransferredbydifferentlinkprotocolsoverdifferentlinks:.,onfirstlink,framerelayonintermediatelinks,.,mayormaynotproviderdtoverlinktransportationanalogy:tripfromPrincetontoLausannelimo:PrincetontoJFKplane:JFKtoGenevatrain:ourist=municationlinktransportationmode=linklayerprotocoltravelagent=routingalgorithmLinkLayer5-*Linklayerservicesframing,ess:encapsulatedatagramintoframe,addingheader,essifsharedmedium“MAC”addressesusedinframeheaderstoidentifysource,destdifferentfromIPaddress!reliabledeliverybetweenadjacentnodeswelearnedhowtodothisalready(chapter3)!seldomusedonlowbit-errorlink(fiber,sometwistedpair)wirelesslinks:higherrorratesQ:whybothlink-levelandend-endreliability?LinkLayer5-*flowcontrol:pacingbetweenadjacentsendingandreceivingnodeserrordetection:errorscausedbysignalattenuation,:signalssenderforretransmissionordropsframeerrorcorrection:receiveridentifiesandcorrectsbiterror(s)withoutresortingtoretransmissionhalf-duplexandfull-duplexwithhalfduplex,nodesatbothendsoflinkcantransmit,butnotatsametimeLinklayerservices(more)LinkLayer5-*Whereisthelinklayerimplemented?ineachandeveryhostlinklayerimplementedin“adaptor”(workinterfacecardNIC)card,;chipsetimplementslink,physicallayerattachesint