Chapter1 Intro to Computer network.

Introduction1-1Chapter1IntroductionComputerNetworking:ATopDownApproach,5thedition.JimKurose,KeithRossAddison-Wesley,April2009.Anoteontheuseofthesepptslides:We’remakingtheseslidesfreelyavailabletoall(faculty,students,readers).They’reinPowerPointformsoyoucanadd,modify,anddeleteslides(includingthisone)andslidecontenttosuityourneeds.Theyobviouslyrepresentalotofworkonourpart.Inreturnforuse,weonlyaskthefollowing:Ifyouusetheseslides(e.g.,inaclass)insubstantiallyunalteredform,thatyoumentiontheirsource(afterall,we’dlikepeopletouseourbook!)Ifyoupostanyslidesinsubstantiallyunalteredformona(orperhapsidenticalto)ourslides,andnoteourcopyrightofthismaterial.Thanksandenjoy!JFK/KWRAllmaterialcopyright1996-2009J.FKuroseandK.W.Ross,AllRightsReservedIntroduction1-2Chapter1:IntroductionOurgoal:get“feel”andterminologymoredepth,detaillaterincourseapproach:useInternetasexampleOverview:what’stheInternet?what’saprotocol?networkedge;hosts,accessnet,physicalmedianetworkcore:packet/circuitswitching,Internetstructureperformance:loss,delay,throughputsecurityprotocollayers,servicemodelshistoryIntroduction1-3Chapter1:roadmap1.1WhatistheInternet?1.2Networkedgeendsystems,accessnetworks,links1.3Networkcorecircuitswitching,packetswitching,networkstructure1.4Delay,lossandthroughputinpacket-switchednetworks1.5Protocollayers,servicemodels1.6Networksunderattack:security1.7HistoryIntroduction1-4What’stheInternet:“nutsandbolts”viewmillionsofconnectedcomputingdevices:hosts=endsystemsrunningnetworkappsHomenetworkInstitutionalnetworkMobilenetworkGlobalISPRegionalISProuterPCserverwirelesslaptopcellularhandheldwiredlinksaccesspointscommunicationlinksfiber,copper,radio,satellitetransmissionrate=bandwidthrouters:forwardpackets(chunksofdata)Introduction1-5“Cool”internetappliancesWorld’ssmallestwebserver~shri/iPic.htmlIPpictureframe’stheInternet:“nutsandbolts”viewprotocolscontrolsending,receivingofmsgse.g.,TCP,IP,HTTP,Skype,EthernetInternet:“networkofnetworks”looselyhierarchicalpublicInternetversusprivateintranetInternetstandardsRFC:RequestforcommentsIETF:InternetEngineeringTaskForceHomenetworkInstitutionalnetworkMobilenetworkGlobalISPRegionalISPIntroduction1-7What’stheInternet:aserviceviewcommunicationinfrastructureenablesdistributedapplications:Web,VoIP,email,games,e-commerce,filesharingcommunicationservicesprovidedtoapps:reliabledatadeliveryfromsourcetodestination“besteffort”(unreliable)datadeliveryIntroduction1-8What’saprotocol?humanprotocols:“what’sthetime?”“Ihaveaquestion”introductions…specificmsgssent…specificactionstakenwhenmsgsreceived,orothereventsnetworkprotocols:machinesratherthanhumansallcommunicationactivityinInternetgovernedbyprotocolsprotocolsdefineformat,orderofmsgssentandreceivedamongnetworkentities,andactionstakenonmsgtransmission,receiptIntroduction1-9What’saprotocol?ahumanprotocolandacomputernetworkprotocol:Q:Otherhumanprotocols?HiHiGotthetime?2:00TCPconnectionrequestTCPconnectionresponseGet:roadmap1.1WhatistheInternet?1.2Networkedgeendsystems,accessnetworks,links1.3Networkcorecircuitswitching,packetswitching,networkstructure1.4Delay,lossandthroughputinpacket-switchednetworks1.5Protocollayers,servicemodels1.6Networksunderattack:security1.7HistoryIntroduction1-11Acloserlookatnetworkstructure:networkedge:applicationsandhostsaccessnetworks,physicalmedia:wired,wirelesscommunicationlinksnetworkcore:interconnectedroutersnetworkofnetworksIntroduction1-12Thenetworkedge:endsystems(hosts):runapplicationprogramse.g.Web,emailat“edgeofnetwork”client/serverpeer-peerclient/servermodelclienthostrequests,receivesservicefromalways-onservere.g.Webbrowser/server;emailclient/serverpeer-peermodel:minimal(orno)useofdedicatedserverse.g.Skype,BitTorrentIntroduction1-13AccessnetworksandphysicalmediaQ:Howtoconnectendsystemstoedgerouter?residentialaccessnetsinstitutionalaccessnetworks(school,company)mobileaccessnetworksKeepinmind:bandwidth(bitspersecond)ofaccessnetwork?sharedordedicated?telephonenetworkInternethomedial-upmodemISPmodem(e.g.,AOL)homePCcentralofficeUsesexistingtelephonyinfrastructureHomeisconnectedtocentralofficeupto56Kbpsdirectaccesstorouter(oftenless)Can’tsurfandphoneatsametime:not“alwayson”Dial-upModemtelephonenetworkDSLmodemhomePChomephoneInternetDSLAMExistingphoneline:0-4KHzphone;4-50KHzupstreamdata;50KHz-1MHzdownstreamdatasplittercentralofficeDigitalSubscriberLine(DSL)Alsousesexistingtelephoneinfrastrutureupto1Mbpsupstream(todaytypically256kbps)upto8Mbpsdownstream(todaytypically1Mbps)dedicatedphysicallinetotelephonecentralofficeIntroduction1-16Residentialaccess:cablemodemsDoesnotusetelephoneinfrastructureInsteadusescableTVinfrastructureHFC:hybridfibercoaxasymmetric:upto30Mbpsdownstream,2MbpsupstreamnetworkofcableandfiberattacheshomestoISProuterhomess