资源描述：
《state of art of ip telephony and mpls》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、7StateofartofIPtelephonyandMPLSL.Subirats,TelematicsEngineeringDept.,TechnicalUniversityofCataloniaAbstract—Thereareseveralqualityofservice(QoS)requirementsinordertoprovideahigh–qualityvoiceoverIP(VoIP)call.Initially,QoSschemeswheredefinedfortheTCP/IPnetworkswithIntegratedS
2、ervice(IntServ)architectureandthenasDifferentiatedServices(DiffServ)architecture.However,theTCP/IPnetworksoperateonthehop–by–hopbasisandcannotprovideacomprehensiveTrafficEngineering(TE)asMultiprotocolLabelSwitching(MPLS)does.AlthoughIP/MPLStechnologywillbeatthecoreofmultise
3、rvicenetworksandisthefuture,MPLSisstillmaturing.QoSstandardsnowassociatedtoATMandtrafficdimensioningofTelephonyoverMPLS(ToMPLS),mustbeimproved;sothereisresearchtodointhisfield.SinceVoIPisthesolutionavailableandismostlikelytobeimplementedintheevolutionfromATMtoMPLS,itwouldbe
4、naturalonalaterstagetoevolvefromVoIPtoVoMPLSinthecorenetwork.IndexTerms—Telephony;MPLS;VoIP;QoS;SLAI.INTRODUCTIONTHereisaplethoraofpublishedpapersdescribingthefactorsinvolvedinahigh–qualityVoIPcall.Thesefactorsincludethespeechcodec,packetization,packetloss,delay,delayvariat
5、ion,andthenetworkarchitecturetoprovidequalityofservice(QoS).OtherfactorsinvolvedinmakingasuccessfulvoiceoverIP(VoIP)callincludethecallsetupsignalingprotocol,calladmissioncontrol,securityconcernsandtheabilitytotraversenetworkaddresstranslation(NAT)andfirewall.AlthoughVoIPinv
6、olvesthetransmissionofdigitizedvoiceinpackets,thetelephoneitselfmaybeanalogordigital.Thevoicemaybedigitizedandencodedeitherbeforeorconcurrentlywithpacketization.Fig.1showsabusinessinwhichaPrivateBranchExchange(PBX)isconnectedtoVoIPgatewaysaswellastothelocaltelephonecompanyc
7、entraloffice[4].Fig.1.BusinessuseofVoIPInitially,QoSschemesweredefinedfortheTCP/IPnetworks,firstastheIntegratedServices(IntServ)architecturewiththeResourcereservationprotocol(RSVP)signaling,andthenastheDifferentiatedServices(DiffServ)architecture.However,theTCP/IPnetworksop
8、erateonthehop–by–hopbasisandcannotprovideacomprehensiveTrafficEngineering(TE).TheM
