Chapter1CommunicationNetworksandServices1.1EvolutionofNetworkArchitectureandServices

1.1.1TelegraphNetworksandMessageSwitching 1.1.2TelephoneNetworksandCircuitSwitching 1.1.3TheInternet,ComputerNetworks,andPacketSwitching1.2FutureNetworkArchitectureandTheirServices1.3KeyFactorsinCommunicationNetworkEvolution 1.3.1RoleofTechnology 1.3.2RoleofRegulation 1.3.3RoleoftheMarket 1.3.4Roleofstandards1.1EvolutionofNetworkArchitectureandServices

Acommunicationnetwork,asetofequipmentandfacilities:Telephonenetwork:bidirectionaltransferofvoicesignalsTelegraphynetworkBroadcastnetworkCellularnetwork；femtocellInternet,andsoon.Thedesignofanetworkisinfluencedbytheservicesthatitsupports1.1EvolutionofNetworkArchitectureandServicesHowandinwhatforminformationistransferred?·Telegraphnetworksandmessageswitching·Telephonenetworksandcircuitswitching·TheInternet,Computernetworks,andPacketswitching1.1.1Telegraphnetworksandmessageswitching

In1837Morsetelegraph·Messagedotsanddashesshortandlongpulses(digitalcommunication)In1851networksoftelegraphstations·routing,address,store-and-forward,messageswitching·routing,address,store-and-forwardingbaseofcomputernetworks·transmissionrate,multiplexing,ASCIIcode,modulationbasisfortoday’smodemsIn1901Marconi,long-distancewirelessradiocommunication1.1.1Telegraphnetworksandmessageswitching1.1.1TelegraphnetworksandmessageswitchingArchitectureoftelegraphnetwork:·digitaltransmission,dotanddash,zeroandone,wire,wirelessorsmokesignal·framing,groupingthesequenceofdots/dashesorzeros/onesintocharactersandmessages

·address,routing1.1.2TelephonenetworksandcircuitswitchingIn1876Bell,telephone,two-way,realtime,simple,analogtransmissionoriginallyIn1878telephoneswitcheswereintroduced.L=N(N-1)/2ifN=1000,L=499500(lines)

1.1.2TelephonenetworksandcircuitswitchingThetelephoneswitchhasthreephases:setup,maintainandtransfer,release1.1.2TelephonenetworksandcircuitswitchingIn1890sautomatedelectromechanicalswitcheswereinvented,hierarchicalnetwork,1.1.2TelephonenetworksandcircuitswitchingTelephonenumberingsystem:fordialingconnectionConnection-oriented:needaconnectionforthetransferofinformationCircuitswitch:thetransfermodethatinvolvessettingupadedicatedend-to-endconnectionOnlyinthesetupphasetheroutingdecisionismade1.1.2TelephonenetworksandcircuitswitchingAnalogtodigitalandcomputerizing ·In1948thetransistorwasinvented.·In1960sintegratedcircuits,leadingtovoicecarriedinadigital transmissionsystem.PCM.T-1(1.5mbps)withthemultiplexing of24PCMsignalsin1962.analogswitch.·Intheearly1980sdigitalswitchesweredeployed.Usertothe networkisonlyanalogtechnology. ·Inthe1960sand1970sswitchwascomputerized,leadingtoa separatesignalingnetwork.Itenabledtheintroduceofnew servicessuchascellulartelephoneserviceetc.1.1.2TelephonenetworksandcircuitswitchingThecharacteristicsofthetelephonenetwork:·transmissionsystem,analogordigital·telephoneswitch,end-to-end·atelephonenumberingsystem·user-to-networksignalingsystem·routingItisnoteworthythatthecontrolpartofthetelephonenetwork,thesignalingsystem,involvescomputercommunication.1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheInternetisbasedofTCP/IP,datagramservice.Thedevelopmentofcomputernetwork:

·SAGEfrom1950to1956,23computernetworks.·SABREin1964,airlinereservationsystem.·Earlycomputerswereextremelyexpensivetree-topology,terminal- orientednetworksin1960s.dumbterminals.

·theARPANETinterconnectedfirstlycomputersoverawidearea. intelligentcomputers.

·theInternet,Inlate1970sTCP/IPemerged,basisfor today’sInternet,IPovereverything.1.1.3TheInternet,ComputerNetworks,andPacketSwitching?1969ARPANET?1974Firstpaperonpacketswitching?1983TCP/IPimplementation?1985NSFNET?1986Firstrouter?1991WWW?1995UScommercialInternet?1996USNextGenerationInternet---->>>>>1.1.3TheInternet,ComputerNetworks,andPacketSwitchingProtocol:

asetofrulesthatgovernshowtwoormorecommunicatingpartiesaretointeract.Including: -messageexchange -Eventaction -Timesequencewhencertainmessagesaretransmittedandreceived.**Computerscommunicationprotocolsmustbepreciseandunambiguous.ProtocolElementsSyntax（語法）=>HowtoSay?Semantic（語義）=>What’sthemeaning?Synchronization（同步）=>Dowhat?1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTerminal-orientednetworks1.1.3TheInternet,ComputerNetworks,andPacketSwitching*Mediumaccesscontrol sharingamulti-dropline1.1.3TheInternet,ComputerNetworks,andPacketSwitching*Statisticalmultiplexer/concentrators:Framing,header,address,error-control,CRC multiplexersystems1.1.3TheInternet,ComputerNetworks,andPacketSwitchingAexampleofterminal-orientednetworks:circa19701.1.3TheInternet,ComputerNetworks,andPacketSwitchingArchitectureofterminal-oriented:AdigitaltransmissionsystemFraming,address,errorcontrolandtheboundariesofaframeMediumaccesscontrol1.1.3TheInternet,ComputerNetworks,andPacketSwitchingComputer-to-computernetworks:packet-switchingnetworksApacketisavariable-lengthblockofinfo.·maximumsize·segmented·multiplepackets·reassembled· 1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheARPANET:

·Inthe1960s,computernetworks,packetswitching,WAN.·Thecommunicationlineswereleasedfrompubliccarriers.·56kbpsdigitaltransmission,upto8000bitsinlength,messagesegmentandreassemble·connectionlessservice,destinationaddressinfoinpacketforrouting,eachpacketswitchcontainsaroutingtable,

·packetframe,errorcontrol,atimeforframeretransmission,·distributedroutingalgorithm,routingtableupdatedinresponsetochangesintrafficortopology

1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheARPANET:1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheARPANET:

·buffering,end-to-endcongestioncontrol,flowcontrol,

·multipleuserapplications,e-mail,remotelogin,filetransferTheARPANETwasthefirstlarge-scalewide-areapacket-switchingnetwork.Itprovidedforthetransferofmessagesbetweenhostcomputersusingconnectionlesspacketswitchingnetwork.Itsarchitectureincorporatedmostoftheelementsofmodernpacketswitchingnetworks1.1.3TheInternet,ComputerNetworks,andPacketSwitchingLocalareanetworks·limiteddistances,shareresource,lowcost,veryhighspeed,relativelyerror-free,theNICagloballyuniqueaddressandmessagesbroadcast.MAC(mediumaccesscontrol),avarietyoftopologyincludingring,bus,treeetc.·theEthernetisthemostsuccessfulLAN1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheEthernet:a)bustopologyb)startopology1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheEthernet:·CSMA/CDcarriersensingmultiple-pointaccess/collisiondetect·thebustopologythestartopology,coaxialcablehubTheelementsofLAN:

·highspeeddigitaltransmissionsystem,·uniqueaddress·frame,mac·supportingbroadcasting1.1.3TheInternet,ComputerNetworks,andPacketSwitchingTheInternet:·inthemid-1970saftertheARPANET,forcommunicationsacrossmultiple,possiblydissimilar,networks.aninternetworkorinternet:

TheInternetProtocols1、TheInternetProtocol(IP):·datagram,theIPpacketswitchesarecalledgatewaysorrouters.·best-effortservice,simplicityinnetworks,complexityonterminals·hierachicaladdressspace,4bytes,dotted-decimalnotation,networkIDandhostID,DNS2、UDPandTCP·userdatagramprotocol,transmissioncontrolprotocol·connectionless-oriented,connection-oriented·existonlyonterminals1.1.3TheInternet,ComputerNetworks,andPacketSwitching3、theapplications·SMTPfore-mail,FTPforfiletransfer,HTTPforwebservice,RTPforreal-timetransfer,etc.·baseofTCP/IP,twoadvantages:1)workovertheentireInternet,2)noeffectontheunderlyingnetworktechnologychange1.1.3TheInternet,ComputerNetworks,andPacketSwitchingThekeyelementsoftheInternet:

·logicallylinkedtogetherbyaglobaluniquespacebasedontheIP·communicationusingTCP/IPsuiteorotherIP-compatibleprotocol·high-levelserviceslayeredonthecommunicationandrelatedinfrastructureNOTE:useTCP/IPandaprivateaddressspaceisreferredtoasaninternet(withlowercasei)ESSENTIALELEMENTOFANETWORKARCHITECTUREDigitaltransmissionforbinaryinfoFraming,delineation,error-controlMediumaccesscontrolAddressesRoutingtableinpacketswitchesforexchangeofpacketsDynamiccalculationofroutingtableCongestioncontrolInternetworkingbyusinggatewaysorroutersSegmentationandreassembly,end-to-enderrorrecoveryAmultiplicityofapplicationsESSENTIALELEMENTOFANETWORKARCHITECTURENote:Theaboveelementscanbeorganizedinalayeredfashion.Twofundamentallyapproachestocommunication:Connectionless:noconnectionneedstobesetupaheadoftime.telegramanddatagramConnection-oriented:aconnectionneedstobesetupbeforeinfocanbetransferred.TelephoneandATM1.2FUTURENETWORKARCHITECTURESANDTHEIRSERVICESTelephone-centrictocomputer-centricnetworksNewapplicationsandservicesnetworkevolutionTheInternetprovidesasimplebutpowerfulservice.AnyapplicationthroughtheexchangeofmessagesMultimediainfoaffectsnetworksevolutiontodayNewprotocolsintheInternetmanagetrafficflowandestablishpathsforIPpacketstoprovidedelayguarantees1.3KEYFACTORSINCOMMUNICATIONNETWORKEVOLUTIONAnewtelecommunicationsserviceshallsatisfywiththreeconditions:Thetechnology:cost-effectiveGovernmentregulations:admittanceThemarket:existAddition:standards1.3KEYFACTORSINCOMMUNICATIONNETWORKEVOLUTIONTechnology,regulation,market,andstandards1.3.1Roleoftechnologywhatcanbebuilt,capab