L17-1

Lesson17IPandDNSText1

RoutingProtocolsandtheClassificationsKeyPoints要點(diǎn)直接的自治系統(tǒng)、路由聚合EGP、IGP、IGRP、RIP、OSPF、IS-ISExterior/interiorSpecial、specific、specify理解課文Aroutingprotocolspecifies規(guī)定howrouterscommunicatewitheachother,disseminating傳播informationthatenablesthemtoselectroutesbetweenanytwonodesonacomputernetwork.Routingalgorithmsdeterminethespecific具體的choiceofroute.Eachrouterhasapriori

先前的knowledgeonlyofnetworksattachedtoitdirectly.Aroutingprotocolsharesthisinformationfirstamongimmediateneighbors,andthenthroughoutthenetwork.Thisway,routersgainknowledgeofthetopologyofthenetwork.ManyroutingprotocolsaredefinedindocumentscalledRFCs.SomeversionsoftheOpenSystemInterconnection(OSI)networkingmodeldistinguishroutingprotocolsinaspecial特別的sublayeroftheNetworkLayer(Layer3).Thespecificcharacteristicsofroutingprotocolsincludethemannerinwhichtheyavoidroutingloops,themannerinwhichtheyselectpreferred更合意

routes,usinginformationabouthop跳轉(zhuǎn)costs,thetimetheyrequiretoreachroutingconvergence,theirscalability,andotherfactors.Althoughtherearemanytypesofroutingprotocols,threemajorclassesareinwidespreaduseonIPnetworks:Interiorgatewayprotocols(IGP)type1,link-stateroutingprotocols,suchasOSPFandIS-IS.Interiorgatewayprotocolstype2,distance-vectorroutingprotocols,suchasRoutingInformationProtocol(RIP),RIPv2,IGRP.Exteriorgatewayprotocols,path-vectorroutingprotocol,suchasBorderGatewayProtocol(BGP).ExteriorgatewayprotocolsareroutingprotocolsusedontheInternetforexchangingroutinginformationbetweenAutonomousSystemswhileinteriorgatewayprotocolswithineachofthem.Anotherwayofclassifyingroutingprotocolsisbythetypeofalgorithmtheyusetodeterminethebestpathtoadestinationnetwork.Routingprotocolscanbeclassifiedasdistancevector,linkstate,orpathvector.Pleasenotice:theterm“Exteriorgatewayprotocol(EGP)”hastwomeanings.ItcouldmeanacategoryofprotocolsusedtoexchangeroutinginformationbetweenAutono