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1、Network Layer4-1Chapter 4a,Network Layer(IP Addresses)Computer Networking:A Top Down Approach Featuring the Internet,5th edition.Jim Kurose,Keith RossAddison-Wesley,July 2021.A note on the use of these ppt slides:Were making these slides freely available to all(faculty,students,readers).Theyre in Po
2、werPoint form so you 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(e.g.,in a class)in substantially unaltered form,that you mention their
3、 source(after all,wed like people to use our book!)If you post any slides in substantially unaltered form 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!JFK/KWRAll material copyright 1996-2021J.F Kuro
4、se and K.W.Ross,All Rights ReservedModified by John CopelandGeorgia Techfor use in ECE3600 Network Layer4-2Chapter 4:Network LayerChapter goals:runderstand principles behind network layer services:mnetwork layer service modelsmforwarding versus routingmhow a router worksmrouting(path selection)mdeal
5、ing with scalemadvanced topics:IPv6,mobilityrinstantiation,implementation in the InternetNetwork Layer4-3Chapter 4:Network Layerr4.1 Introductionr4.2 Virtual circuit and datagram networksr4.3 Whats inside a routerr4.4 IP:Internet ProtocolmDatagram formatmIPv4 addressingmICMPmIPv6r4.5 Routing algorit
6、hmsmLink statemDistance VectormHierarchical routingr4.6 Routing in the InternetmRIPmOSPFmBGPr4.7 Broadcast and multicast routingNetwork Layer4-4Network layerrtransport segment from sending to receiving host ron sending side encapsulates segments into datagramsron receiving side,delivers segments to
7、transport layerrnetwork layer protocols in every host,routerrRouter examines IP header fields in all IP datagrams passing through itnetworkdata linkphysicalnetworkdata linkphysicalnetworkdata linkphysicalnetworkdata linkphysicalnetworkdata linkphysicalnetworkdata linkphysicalnetworkdata linkphysical
8、networkdata linkphysicalapplicationtransportnetworkdata linkphysicalapplicationtransportnetworkdata linkphysicalNetwork Layer4-5Two Key Network-Layer Functionsrforwarding:move packets from routers input to appropriate router outputrrouting:determine route taken by packets from source to dest.mroutin
9、g algorithmsanalogy:rrouting:process of planning trip from source to destrforwarding:process of getting through single interchangeNetwork Layer4-61230111value in arrivingpackets headerrouting algorithmlocal forwarding tableheader value output link01000101011110013221Interplay between routing and for
10、wardingThe Routing Algorithm is used to calculate the link-IDs in the Forwarding Table.When a datagram arrives,the destination IP address is used to lookup the output link-ID.Network Layer4-7Connection setupr3rd important function in some network architectures:mATM,frame relay,X.25(but not IP)rbefor
11、e datagrams flow,two end hosts and intervening routers establish virtual connectionmrouters get involvedrnetwork vs transport layer connection service:mnetwork:between two hosts(may also involve intervening routers in case of VCs)mtransport:between two processesNetwork Layer4-8Network service modelQ
12、:What service model for“channel transporting datagrams from sender to receiver?Example services for individual datagrams:guaranteed deliveryguaranteed delivery with less than 40 msec delay“best effort(e.g.,IP)Example services for a flow of datagrams:rin-order datagram deliveryrguaranteed minimum ban
13、dwidth to flowrrestrictions on changes in inter-packet spacingNetwork Layer4-9ATM Network layer service models:NetworkArchitectureInternetATMATMATMATMServiceModelbest effortCBRVBRABRUBRBandwidthnoneconstantrateguaranteedrateguaranteed minimumnoneLossnoyesyesnonoOrdernoyesyesyesyesTimingnoyesyesnonoC
14、ongestionfeedbackno(inferredvia loss)nocongestionnocongestionyesnoGuarantees?ATM=Asynchronous Transfer ModeNetwork Layer4-10Chapter 4:Network Layerr4.1 Introductionr4.2 Virtual circuit and datagram networksr4.3 Whats inside a routerr4.4 IP:Internet ProtocolmDatagram formatmIPv4 addressingmICMPmIPv6r
15、4.5 Routing algorithmsmLink statemDistance VectormHierarchical routingr4.6 Routing in the InternetmRIPmOSPFmBGPr4.7 Broadcast and multicast routingNetwork Layer4-11Network layer connection and connection-less servicerdatagram network provides network-layer connectionless servicerVC network provides
16、network-layer connection serviceranalogous to the transport-layer services,but:mservice:host-to-hostmno choice:network provides one or the othermimplementation:in network coreNetwork Layer4-12Virtual circuitsrcall setup,teardown for each call before data can flowreach packet carries VC identifier(not destination host address)revery router on source-dest path maintains“state for each passing connectionrlink,router resources(bandwidth,buffers)may be allocated to VC(dedicated resources=predictable
