1、ATMNew words and phrases 1 asynchronous adj.异步的,不同时的 Asynchronous Transfer Mode 异步转移模式2 forum n.论坛,讨论会3 consortium n.社团,协会,联盟,(国际)财团4 release vt.发表(消息);出版5 consultant n.顾问,商议者,咨询者6 promote vt.推广,宣传7 rationale n.基本原理8 unify vt.统一,使成一体 9 escalate vt.使逐步上升10 scalable adj.可升级的11 cell n.信元12 ubiquitous a
2、dj.无所不在的，普遍存在的13 static adj.固定的,变化小的ATM14 amortize(amortise)vt.分期偿付15 merge vt.合并,兼并 merger n.合并,结合 16 multiplexer n.多路(复用)器17 interim n.中间时期,过渡时期18 wreak vt.带来,引起19 havoc n.大破坏,浩劫20 ether n.以太 ethernet n.以太网21 latency n.等待时间,延迟时间22 payload n.有效载荷23 field n.字段24 congestion n.拥挤,拥塞25 discard n.丢弃;删除2
3、6 eligible n.合格者,人选ATM1 cell switching 信元交换；蜂窝站点切换2 circuit switched network 电路交换网络3 switch network 交换网络 switching network 开关网络，转换网络4 highspeed digital transmission 高速数据传输5 frame relay 帧中继6 PBX（private branch exchange)专用小交换机7 tokenring LAN 令牌环局域网 tokenring 令牌环ATM8 connectionoriented 面向连接的9 CBR（const
4、ant bit rate)恒比特率10 QoS(quality of service)服务质量11 IP(Internet Protocol)Internet协议,互联网协议12 virtual path 虚拟路径 VPI（Virtual Path Identifier）虚路径标识符13 VC(virtual channel)虚信道,虚通路14 ATM switchATM 交换机15 CLP(Cell Loss Priority)信元丢失优先权（级）16 CRC(Cyclic Redundancy Check)循环冗余校验ATMEvolution Asynchronous Transfer M
5、ode(ATM)represents a communications technology designed to overcome the constraints associated with traditional and,for the most part,separate voice and data networks.ATM has its roots in the work of a CCITT(nowknown as ITU-T)study group formed to develop broadband ISDN standards during the mid1980s
6、.In 1988,a cell switching technology was chosen as the foundation for broadband ISDN,and in 1991,the ATM Forum was founded.The ATM Forum represents an international consortium of public and private equipment vendors,data communications and telecommunications service providers,consultants,and end use
7、rs established to promote the implementation of ATM.To accomplish this goal,the ATM Forum develops standards with the ITU and other standards organizations.The first ATM Forum standard was released in 1992.Various ATM Forum working groups are busy defining additional ATMstandards required to enable
8、ATM to provide a communications capability for the wide range of LAN and WAN transmission schemes it is designed tosupport.This standardization effort will probably remain in effect for a considerable period due to the comprehensive design goal of the technology,which was developed to support voice,
9、data,and video on bothlocal and wide area networks.The Rationale for ATM and Its Underlying Technology ATM can be considered to represent a unifying technology because it was designed to transport voice,data,and video(including graphics images)on both local and wide area networks.Until the developme
10、nt of ATM,networks were normally developed based on the type of data to be transported.Thus,circuit switched networks,which included the public switched telephone network and high speed digital transmission facilities,were primarily used to transport delay sensitive information,such as voice and vid
11、eo.In comparison,on packet based networks,such as X.25 and Frame Relay,information can tolerate a degree of delay.Network users can select a networking technology ATMto satisfy a specific communications application,but most organizations support a mixture of applications.Thus,most organizations are
12、forced to operate multiple networks,resulting in a degree of inefficiency and escalating communications costs.By combining the features from both technologies,ATM enables a single network to support voice,data,and video.ATM is designed to be scalable,enabling its 53 byte cell to be transported from
13、LAN to LAN via WAN,as well as for use on publicand private wide area networks at a range of operating rates.On LANs,ATM support is currently offered at 25and 155 Mbps,whereas access to WAN based ATM carrier networks can occur at T1(1.544 Mbps),at T3(45 Mbps),or via different SONET facilities at data
14、 rates such as 622 Gbps,all based on the transportation of 53 byte cells.A key to ATMs ubiquitous transmission capability is its fixed 53 byte cell length,which remains static regardless of changes in media,operating rates,or framing.Exercises.Please translate the following words and phrases into Ch
15、inese.1.highspeed digital transmission2.broadband ISDN3.international consortium4.VCI 5.Cell Loss Priority(CLP)6.CRC 7.PBX 8.QoS 9.tokenring LAN 10.circuit switched network11.PTI12.CBR高速数据传输高速数据传输宽带综合业务数字网（宽带综合业务数字网（broadband Integrated Services Digital Network)国际社团国际社团虚信道标识符虚信道标识符(Virtual Channel I
16、dentifier)信元丢失优先权（级）信元丢失优先权（级）循环冗余校验循环冗余校验(Cyclic Redundancy Check)专用小交换机专用小交换机(private branch exchange)服务质量服务质量(Quality of Service)令牌环局域网令牌环局域网(tokenring local area network)电路交换网络电路交换网络 有效负荷类型标识符有效负荷类型标识符(Payload Type Identifier)恒比特率恒比特率(constant bit rate)Exercises.Please translate the following wo
17、rds and phrases into English.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Asynchronous Transfer Mode(ATM)wide area networksFrame Relaypacketbased networkscell headerconnectionorientedInternet Protocol(IP)ethernetvirtual channels(VCs)ATM Forum virtual pathcircuit swit
18、ched networkExercises.Fill in the blanks with the missing word(s).1.ATM has its roots in the work of a CCITT(now known as ITU-T)study group formed to develop broadband ISDN standards during the mid1980s.2.ATM is designed to be scalable,enabling its 53byte cell to be transported(transport,be transpor
19、ted,transporting)from LAN to LAN via WAN,as well as for use on public and private wide area networks at a range of operating rates.3.For example,traffic from a router connected to a LAN might be fed into/to a port on a highspeed multiplexer with another connection to the multiplexer from the company
20、 PBX.4.Instead of being wasted,its space can be used to expand the length of the Virtual Path Identifier field.5.A key to ATMs ubiquitous transmission capability is its fixed 53byte cell length,which remains static regardless of changes in media,operating rates,or framing.Exercises6.ATM is based on
21、the switching of 53byte cellsin which each cell consists of a 5byte header and a payload of 48 bytes of information.7.Recognizing the differences among voice,video,and data transportation,ATM was designed to adapt to the time sensitivity of different applications.8.In a data communications environme
22、nt,the network can range in scope from an Ethernet or tokenring LAN to an X.25 or Frame Relay WAN.9.ATM can be considered to represent a unifying(unifying，unify，unified）technology because it was designed to transport(transport,transporting)voice,data,and video(including graphics images)on both local
23、 and wide area networks.10.If the cell cannot be discarded,the CLP field bit is set(is set,set)to 0.Exercises.Answer the following questions according to the text.1.What is the initial purpose of ATM?ATM has its roots in the work of a CCITT(now known as ITUT)study group formed to develop broadband I
24、SDN standards during the mid1980s.2.What is ATM Forum?What is its work?The ATM Forum represents an international consortium of public and privateequipment vendors,data communications and telecommunications service providers,consultants,and end users established to promote the implementation of ATM.V
25、arious ATM Forum working groups are busy defining additional standards required to enable ATM to provide a communications capability for the wide range of LAN and WAN transmission schemes it is designed to support.3.What technologies does ATM use?ATM uses both circuit switched networks and packetbas
26、ed networks technologies,it enables a single network to support voice,data,and videoExercises4.What are the characters of ATM?ATM is designed to be scalable,enabling its 53byte cell to be transported from LAN to LAN via WAN,as well as for use on public and private wide area networks at a range of op
27、erating rates.The use of a fixedlength cell enables low cost hardware to be developed to perform required cell switching based on the contents of the cell header,without requiring more complex and costly software.5.Which types of interfaces does ATM support?ATM supports two major types of interfaces
28、:NetworktoUser(UNI)and NetworktoNetwork(NNI).6.Please describe the architecture of ATM.ATM is based on the switching of 53byte cellsin which each cell consists of a 5byteheader and a payload of 48 bytes of information.Fig.14.1 illustratesthe format of the ATM cell,including the explosion of its 5byt
29、e header to indicate the fields carried in the header.5byte header include:the 4bit Generic Flow Control(GFC)field,the 8bit Virtual Path Identifier(VPI)field,the Virtual Channel Identifier(VCI),the Payload Type Identifier(PTI)field,the 1bit Cell Loss Priority(CLP)field,the 8bit Header Error Control field,ec
