Unit 15 ATM,异步传输模式,Part Three Communication and Information Processing,Technical terms:,Preparing for the text:,Questions for text discussion: What is ATM short for? It is short for Asynchronous Transfer Mode. 2. Describe how the TDM works. With TDM, each user is assigned to a time plot, and no other user can send in that slot.,1. Asynchronous Transfer Mode (ATM) 异步传输模式 2. Broadband Integrated Services Digital Network (B-ISDN) 宽带综合业务数据网 3. circuit switching 电路交换 4. packet switching 分组交换 5. time-division multiplexing (TDM) 时分多路复用 6. LAN (local area network) 局域网,3. Why do we say that ATM is more efficient than synchronous technology?,Because ATM is asynchronous, time slots are available on demand with information identifying the source the transmission contained in the header of each ATM cell.,The main idea of this unit:,This unit mainly discusses the basic knowledge about “ATM”. (1) ATM is short for Asynchronous Transfer Mode that is an International Telecommunication Union Telecommunications Standards Sections standards for cell relay wherein information for multiple service types. (2) ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching with those of packet switching . (3) ATM supports two types of connections: point-to-point and point-multipoint.,New Words,1.technology n. 复数 technologies The application of science, especially to industrial or commercial objectives. 技术：科学的应用，尤指为了工业或商业的目的 The scientific method and material used to achieve a commercial or industrial objective. 技术：用以达到商业或工业的目的的科学方法和材料,2. multiple adj. 多样的, 多重的 multiple types. 多种类型. 3.standard (1) n. 标准 educational standard 教育标准 (2) adj.合乎标准的 a standard reference 参考标准,4.conceive vt. To form or develop in the mind; devise: 构思：在脑海中设计或构思；设计： conceive a plan to increase profits. 构想出一个增加利润的计划.,5. release vt. 释放 To free from something that binds, fastens, or holds back; let go: 松开，解开：从捆绑、牢系或阻挡的东西中解放出来； 放开： Eg. release the balloons; 放走气球； Eg. release a flood of questions. 提出一大堆问题,6. interface n. 界面. Windows interface 窗口界面 7. guarantee vt. To undertake to do, accomplish, or ensure 承诺，保证：保证去做 guaranteed to free the captives; guarantees freedom of speech. 保证释放犯人；保证言论自由,8. delay (1) To cause to be later or slower than expected or desired: 使延迟：使比期望的要迟一些或慢一些： Heavy traffic delayed us. 交通堵塞使我们迟到了 (2) n.耽搁, 延迟, 迟滞 Time delay 时间滞后,9. packet n. 包 Information packet 10. synchronous adj. 同步的 Synchronous motor 同步电动机,11. Bandwidth n. 带宽 The numerical difference between the upper and lower frequencies of a band of electromagnetic radiation, especially an assigned range of radio frequencies. 带宽：电磁辐射频带中高频与低频之间的数值差，尤指某设 定的无线电频率范围,12. assign vt. To give out as a task; allot. 指派，,分配 The hardest work was assigned to the strongest laborers. 最繁重的工作分配给最强壮的劳工。 13. slot n. 时隙 a new time slot for a TV program. 电视节目的新时段 14. identify vt. 识别, 鉴别 Help me identify this thorny fruit tree! 帮我识别一下这棵多刺的果树。,15. Implement vt. To put into practical effect; carry out: 使生效；执行： implement the new procedures 实施新的程序,Expressions:,1. be based on 基于 2. combine with 把与结合 3. because of 因为,What he said is based on fact. 他所说的话是以事实为根据的。 If your talent combines with diligence, you can excel in your pursuit. 如果你把天赋与勤奋结合起来, 你所追求的事业便会出类拔萃。 I cant go to the party this evening because of the exam . 因为考试我不能去参加今天晚上的晚会了。,Text,Paragraph 1: Asynchronous Transfer Mode (ATM) is an International Telecommunication Union Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells. ATM networks are connection-oriented. 译：异步传输模式是国际电联-电信标准部门为信元中继创建的标准，信元中继中的信息可以是多种业务类型，如语音、视频或数据，他们都将转换为一个个小的固定大小的信元.ATM网络是面向连接的。 Phrases: such as.,Paragraph 2: ATM is based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It was originally conceived as a high-speed transfer technology for voice, video and data over public networks. The ATM Forum extended the ITU-Ts vision of ATM for use over public networks and private networks. The ATM Forum has released work on the following specifications; User-to-Network Interface UNI 2.0, UNI 3.0 , UNI 3.1, UNI 4.0, Public-Network Node Interface(P-NNI), LAN Emulation (LANE), Multiprotocol over ATM. 译:ATM是在ITU-T的款待综合业务数字网（B-ISDN）标准的基础上发展起来的。它最早起源于在公用网络上高速传输语音、视频和数据的技术。ATM论坛扩展了ATM的ITU-T的思想，使它不仅可以用在公用网络，也可以用在私人网络。ATM论坛已经发布了以下工作成果：用户-网络接口UN I2.0，UN I3.0，UN I4.0，公用网络接点接口（P-NNI），局域网仿真（LANE），ATM多协议。Phrases: be based on.,Paragraph 3: ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (guaranteed capacity and constant transmission delay)with those of packet switching (flexibility and efficiency for intermittent traffic). It provides scalable bandwidth from a few megabits per second (Mbps) to many gigabits per second(Gbps). Because of