《通信与电子信息科技英语》课件unit 14

ATMNewwordsandphrases

1asynchronousadj.异步的,不同时的

AsynchronousTransferMode异步转移模式2forumn.论坛,讨论会3consortiumn.社团,协会,联盟,(国际)财团4releasevt.发表(消息);出版5consultantn.顾问,商议者,咨询者6promotevt.推广,宣传7rationalen.基本原理8unifyvt.统一,使成一体9escalatevt.使逐步上升10scalableadj.可升级的11celln.信元12ubiquitousadj.无所不在的，普遍存在的13staticadj.固定的,变化小的

ATM14amortize(amortise)vt.分期偿付15mergevt.合并,兼并

mergern.合并,结合16multiplexern.多路(复用)器17interimn.中间时期,过渡时期18wreakvt.带来,引起19havocn.大破坏,浩劫20ethern.以太

ethernetn.以太网21latencyn.等待时间,延迟时间22payloadn.有效载荷23fieldn.字段24congestionn.拥挤,拥塞25discardn.丢弃;删除26eligiblen.合格者,人选

ATM1cellswitching信元交换；蜂窝站点切换2circuitswitchednetwork电路交换网络3switchnetwork交换网络

switchingnetwork开关网络，转换网络4highspeeddigitaltransmission高速数据传输5framerelay帧中继6PBX（privatebranchexchange)专用小交换机7tokenringLAN令牌环局域网

tokenring令牌环

ATM8connectionoriented面向连接的9CBR（constantbitrate)恒比特率10QoS(qualityofservice)服务质量11IP(InternetProtocol)Internet协议,互联网协议12virtualpath虚拟路径

VPI（VirtualPathIdentifier）虚路径标识符13VC(virtualchannel)虚信道,虚通路14ATMswitchATM交换机15CLP(CellLossPriority)信元丢失优先权（级）16CRC(CyclicRedundancyCheck)循环冗余校验

ATM Evolution AsynchronousTransferMode(ATM)representsacommunicationstechnologydesignedtoovercometheconstraintsassociatedwithtraditionaland,forthemostpart,separatevoiceanddatanetworks.ATMhasitsrootsintheworkofaCCITT(nowknownasITU-T)studygroupformedtodevelopbroadbandISDNstandardsduringthemid1980s.In1988,acellswitchingtechnologywaschosenasthefoundationforbroadbandISDN,andin1991,theATMForumwasfounded.TheATMForumrepresentsaninternationalconsortiumofpublicandprivateequipmentvendors,datacommunicationsandtelecommunicationsserviceproviders,consultants,andendusersestablishedtopromotetheimplementationofATM.Toaccomplishthisgoal,theATMForumdevelopsstandardswiththeITUandotherstandardsorganizations.ThefirstATMForumstandardwasreleasedin1992.VariousATMForumworkinggroupsarebusydefiningadditionalATMstandardsrequiredtoenable

ATMtoprovideacommunicationscapabilityforthewiderangeofLANandWANtransmissionschemesitisdesignedtosupport.Thisstandardizationeffortwillprobablyremainineffectforaconsiderableperiodduetothecomprehensivedesigngoalofthetechnology,whichwasdevelopedtosupportvoice,data,andvideoonbothlocalandwideareanetworks.TheRationaleforATMandItsUnderlyingTechnology

ATMcanbeconsideredtorepresentaunifyingtechnologybecauseitwasdesignedtotransportvoice,data,andvideo(includinggraphicsimages)onbothlocalandwideareanetworks.UntilthedevelopmentofATM,networkswerenormallydevelopedbasedonthetypeofdatatobetransported.Thus,circuitswitchednetworks,whichincludedthepublicswitchedtelephonenetworkandhighspeeddigitaltransmissionfacilities,wereprimarilyusedtotransportdelaysensitiveinformation,suchasvoiceandvideo.Incomparison,onpacketbasednetworks,suchasX.25andFrameRelay,informationcantolerateadegreeofdelay.Networkuserscanselectanetworkingtechnology

ATMtosatisfyaspecificcommunicationsapplication,butmostorganizationssupportamixtureofapplications.Thus,mostorganizationsareforcedtooperatemultiplenetworks,resultinginadegreeofinefficiencyandescalatingcommunicationscosts.Bycombiningthefeaturesfrombothtechnologies,ATMenablesasinglenetworktosupportvoice,data,andvideo.ATMisdesignedtobescalable,enablingits53bytecelltobetransportedfromLANtoLANviaWAN,aswellasforuseonpublicandprivatewideareanetworksatarangeofoperatingrates.OnLANs,ATMsupportiscurrentlyofferedat25and155Mbps,whereasaccesstoWANbasedATMcarriernetworkscanoccuratT1(1.544Mbps),atT3(45Mbps),orviadifferentSONETfacilitiesatdataratessuchas622Gbps,allbasedonthetransportationof53bytecells.AkeytoATM’subiquitoustransmissioncapabilityisitsfixed53bytecelllength,whichremainsstaticregardlessofchangesinmedia,operatingrates,orframing.

ExercisesⅠ.PleasetranslatethefollowingwordsandphrasesintoChinese.1.highspeeddigitaltransmission2.broadbandISDN3.internationalconsortium4.VCI5.CellLossPriority(CLP)6.CRC7.PBX8.QoS9.tokenringLAN10.circuitswitchednetwork11.PTI12.CBR高速数据传输宽带综合业务数字网（broadbandIntegratedServicesDigitalNetwork)国际社团虚信道标识符(VirtualChannelIdentifier)信元丢失优先权（级）循环冗余校验(CyclicRedundancyCheck)专用小交换机(privatebranchexchange)服务质量(QualityofService)令牌环局域网(tokenringlocalareanetwork)

电路交换网络有效负荷类型标识符(PayloadTypeIdentifier)恒比特率(constantbitrate)ExercisesⅡ.PleasetranslatethefollowingwordsandphrasesintoEnglish.1.异步转移模式2.广域网3.帧中继4.分组网5.信元头6.面向连接7.互联网协议8.以太网9.虚通道10.ATM论坛11.虚拟路径12.电路交换网络

AsynchronousTransferMode(ATM)wideareanetworksFrameRelaypacketbasednetworkscellheaderconnectionorientedInternetProtocol(IP)ethernetvirtualchannels(VCs)ATMForumvirtualpathcircuitswitchednetworkExercisesⅢ.Fillintheblankswiththemissingword(s).1.ATMhasitsroots

in

thework

of

aCCITT(nowknownasITU-T)studygroupformedtodevelopbroadbandISDNstandardsduringthemid1980s.2.ATMisdesigned

to

bescalable,enablingits53bytecellto

be

transported(transport,betransported,transporting)fromLANtoLANviaWAN,aswellasforuse

on

publicandprivatewideareanetworksatarangeofoperatingrates.3.Forexample,trafficfromarouterconnectedtoaLANmightbefed

into/to

aportonahighspeedmultiplexerwithanotherconnectiontothemultiplexerfromthecompanyPBX.4.Instead

of

beingwasted,itsspacecanbeusedtoexpandthelengthoftheVirtualPathIdentifierfield.5.AkeytoATM’subiquitoustransmissioncapabilityisitsfixed53bytecelllength,whichremainsstaticregardless

of

changesinmedia,operatingrates,orframing.

Exercises6.ATMisbased

on

theswitchingof53bytecells—inwhicheachcellconsistsofa5byteheaderandapayloadof48bytesofinformation.7.Recognizingthedifferences

among

voice,video,anddatatransportation,ATMwasdesignedtoadapt

to

thetimesensitivityofdifferentapplications.8.Inadatacommunicationsenvironment,thenetworkcanrange

in

scopefromanEthernetortokenringLAN

to

anX.25orFrameRelayWAN.9.ATMcanbeconsideredtorepresenta

unifying

(unifying，unify，unified）technologybecauseitwasdesignedto

transport

(transport,transporting)voice,data,andvideo(includinggraphicsimages)

on

bothlocalandwideareanetworks.10.Ifthecellcannotbediscarded,theCLPfieldbit

isset

(isset,set)to0.

ExercisesⅣ.Answerthefollowingquestionsaccordingtothetext.1.WhatistheinitialpurposeofATM?ATMhasitsrootsintheworkofaCCITT(nowknownasITUT)studygroupformedtodevelopbroadbandISDNstandardsduringthemid1980s.2.WhatisATMForum?Whatisitswork?TheATMForumrepresentsaninternationalconsortiumofpublicandprivateequipmentvendors,datacommunicationsandtelecommunicationsserviceproviders,consultants,andendusersestablishedtopromotetheimplementationofATM.VariousATMForumworkinggroupsarebusydefiningadditionalstandardsrequiredtoenableATMtoprovideacommunicationscapabilityforthewiderangeofLANandWANtransmissionschemesitisdesignedtosupport.3.WhattechnologiesdoesATMuse?ATMusesbothcircuitswitchednetworksandpacketbasednetworkstechnologies,itenablesasinglenetworktosupportvoice,data,andvideoExercises4.WhatarethecharactersofATM?ATMisdesignedtobescalable,enablingits53bytecelltobetrans