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1、UNIT 7 Network Essentials,计算机专业英语,COMPETENCIES,After you have read this unit, you should be able to: Discuss network and communication. Describe local area, metropolitan area, and wide area network. Name LAN devices and WAN devices. Describe common media. Describe the seven layers of the OSI referen
2、ce model. Discuss the main function of each layer of the OSI reference model.,Text A,Network Overview,Concept Check,What is a network? What is a network topology? List four principal network topologies. Name the different types of networking media. List devices for LAN and for WAN.,New Words and Phr
3、ases,installation n. 安装 converge v. (指物体等)会于一点，向一点会合；聚集 spectacular adj. 引人注目的；出色的；与众不同的 profound adj. 深的；深切的；深远的；极度的；极大的 computational adj. using computers 使用计算机的 interconnected adj. (彼此)有联系的；相互依存的 intricate adj. 复杂的 cardiovascular adj. 心血管的：心血管的，与心血管有关的，侵袭心血管的,New Words and Phrases,approach n. 方法；
4、手段 geographic adj. 地理的 metropolitan adj.大城市的 reliable adj. 可信赖的；可靠的 infrared adj. 红外线的 ultraviolet adj. 紫外线的 hierarchical adj. 分层的、分级的、层次的 electromagnetic adj. 电磁的,New Words and Phrases,filter v. 过滤 backbone n. 主干网络；主干线路 due to 因为，由于，归于 refer to .as 称为 depend on sth. 视某事物而定；取决于某事物,Notes,1. Due to ra
5、pid technological progress, these areas are rapidly converging, and the differences between collecting, transporting, storing, and processing information are quickly disappearing. 分析其中后半句中主语、谓语分别是the differences are quickly disappearing ，而介词短语“between collecting, transporting, storing, and processin
6、g information”是主语“the differences”的定语。,Notes,2. The idea that within 20 years equally powerful computers smaller than postage stamps could be mass produced by the millions has become reality. 分析句中去除修饰成分，句子的主干是The idea has become reality，而“idea”之后的that从句是修饰idea的同位语从句。,Notes,3. The old model of a sing
7、le computer serving all of the organizations computational needs has been replaced by one in which a large number of separate but interconnected computers do the job. 分析全句的主要成分是The old model has been replaced by one。句中“of a single computer serving all of the organizations computational needs”是old mo
8、del的后置定语；“in which a large number of separate but interconnected computers do the job”是修饰“one”的。 译文 单个计算机服务于组织中的所有计算需要的旧模式已经被另一种模式取代，在这种模式中许多独立但互连的计算机完成这个工作。,Notes,4. It includes the source information along with other elements that are necessary in order to make communication possible and reliable
9、with the destination device. 分析句中“along with”意思为：in addition to sth 除某事物以外；“it”指“data packet”； 译文 数据包包含源信息以及其它元素，这些元素是使源与目标设备之间的通讯正常、可靠所必须的。,Notes,5. A Protocol is a set of rules that make communication on a network more efficient. 分析句中“a set of sth.”意为：group of similar things that belong together i
10、n some way 一组，一套(类似物品) 译文 协议是一组规则，它使得网络通讯更高效。,Text B,The OSI Reference Model,Concept Check,Why is the OSI reference model important? Name the seven layers of the OSI reference model.,New Words and Phrases,vendor n. 摊贩；小贩 visualize v. 想像或设想 adjacent adj. 与某物邻近的；接近的；相接触的 node n. 节点；网点；结点 entity n. 实体
11、terminal n. 终端,New Words and Phrases,synchronize v. 使(事件)同时出现；同步 procedure n. 规程；程序；过程 recovery n. 还原、 恢复 integrity n. 完整性 data integrity 数据完整性 regulation n. 规章；规则；法规；条例,New Words and Phrases,provision n. 对策 exception n. 异常 segment v. 分割成部分 deactivate de- 前缀 的反义或否定；除掉 data rate n. 数据率 be concerned w
12、ith sth. 与某事物有关；涉及某事物 full-duplex adj. 全双工,Notes,1. The application layer establishes the availability of intended communication partners, synchronizes and establishes agreement on procedures for error recovery and control of data integrity. 分析全句主语为“ application layer”后跟三个动词“establishes”、“synchroniz
13、es”、“establishes”；“intended”意为：planned, meant, desired 计划的；打算的；意欲的。 译文 应用层建立与欲通讯伙伴的可用连接，同步以及创建有关错误恢复和数据完整性控制规程的约定。,Notes,2. The presentation layer ensures that the information that the application layer of one system sends out is readable by the application layer of another system. 分析句中两个that从句使句子变得
14、复杂了，第一个that从句是从“the information thatanother system”即到句末，它是“ensures”的宾语从句；第二个that从句“the application layer of one system sends out”包含在第一个that从句中，它是从句主语“information”的定语从句。 译文 表示层保证了从一个系统应用层发送出的信息可以被另一系统的应用层读懂。,Notes,3. In addition to session regulation, the session layer offers provisions for efficient
15、 data transfer, class of service, and exception reporting of session layer, presentation layer, and application layer problems. 分析句子结构并不复杂，句子的主干结构是“the session layer offers provisions”，for之后直到句末部分是修饰“provision”的；而“of session layer, presentation layer, and application layer problems”是“reporting”的后置定语
16、。 译文 会话层除了提供会话规则外，还为数据高效传输、服务类型以及会话层、表示层和应用层问题的异常报告提供对策。,Notes,4. The transport layer attempts to provide a data transport service that shields the upper layers from transport implementation details. 译文 传输层提供了数据传输服务，这种服务对高层屏蔽了传输实现的细节。,Notes,5. Specifically, issues such as how reliable transport between two hosts is accomplished is the concern of the transport layer. 分析 全句主干结构为：issues is the concern， 句中“how reliable transport between two hosts is
