计算机专业英语的课文与翻译

精品文档

Unit 8 Computer Networking

Text 1 Data Communications

The end equipment can be computers, printers, keyboards, CRTs, and so on. They are either generates the digital information for transmission or uses the received digital data. This equipment generally operates digital information internally in word units.

DTE is data terminal equipment. A station controller (STACO)is the corresponding unit at the secondaries. At one time, the DTE was the last piece of equipment that belonged to the subscriber in a data link system. Between the DTEs, first is the modem, and then is the communications equipment. The communication equipment is owned and maintained by Telco. Data communications equipment (DCE) accepts the serial data stream from the DTE. And DCE converts it to some form of analog signal suitable for transmission on voice-grade lines. At the receive end, the DCE performs the reverse function. It converts the received analog signal to a serial digital data stream. The simplest form of DCE is a modem (modulator/demodulator) or data set. At the transmit end, the modem can be considered a form of digital-to-analog converter.While at the receive end, it can be considered a form of analog-to-digital converter.

参考译文

数据通信

终端设备可以是计算机、打印机、键盘、CRT等。它们可以生成要发送的数字信息，

随意编辑

精品文档

也可以使用所接收的数字数据。这种设备通常在内部以字为单位处理数字信息。

DTE一般称为数据终端设备。辅助设备一方的相应设备是工作站控制器（STACO）。同时，DTE也是数据链路系统中属于用户端的最后一个设备。在两个DTE之间，先是调制解调器，接着是属于T elco电话公司维护的通信设备。数据通信设备（DCE）从DTE接收串行数据流，并将其转换成适合于在语音线路上发送的某种模拟信号形式。在接收端，DCE完成相反的功能，把接收到的模拟信号转换成串行数字数据流。最简单的DCE是调制解调器或数据传送机。在发送端，调制解调器可以视为一种数/模转换器，而在接收端则可视为一种模／数转换器。

Text 2 Architecture of Computer Networks Computer network is a complex unit, it consists of two or more connected computing units. It is used for the purpose of data communication and resource sharing. Design of a network and its logical structure should comply with a set of design principles. They include: the organization of functions, the description of data formats and procedure.

In the following two sections we will discuss two important network architectures, the OSI reference model and the TCP/IP reference model.

(1)the OSI reference model

The OSI (open systems interconnection) model was created by the ISO. This model is a foundation for comparing protocols; However, more protocols deviate from the rules set up by the OSI model.

The OSI model has seven layers. Note that the OSI model itself is not a network architecture.It just tells what each layer should do. However, ISO has also produced standards for all the layers. Each one has been published as a separate international

随意编辑

精品文档

standard.

(2)the TCP/IP reference model

TCP/IP is a communication protocol; it provides many different networking services.

The TCP/IP Internet protocol suite is formed from two standards: the TCP (Transmission Control Protocol) and the IP (Internet Protocol). TCP means it is on the transport layer. IP means it is on the network layer. On top of the transport layer is the application layer. It contains all the higher-level protocols. The early ones included virtual terminal (TELNET), file transfer (FTP), electronic mail (SMTP)and domain name service (DNS).

As we know, TCP/IP is the foundation of the Internet.These protocols are continually changing and evolving to support the needs of the user community.参考译文

计算机网络结构

计算机网络是由两个或多个计算机设备互连而成的一种复合系统，它用于数据通信和资源共享。网络设计及其逻辑结构应该遵循一套设计原则，其中包括：功能的组织以及数据格式和过程的说明。

在下面的两小节里，我们将讨论两个重要的网络体系结构，即OSI参考模型和TCP/IP 参考模型。

(1)OSI参考模型

OSI模型（开放系统互联参考模型）是由国际标准化组织（ISO）开发的一个建议。相对于其他协议来说，此种模式为基础模式。然而，更多的协议是背离OSI模型的。

随意编辑

精品文档

OSI模型有7层。应该注意的是，OSI模型本身并不是一种网络体系结构，它只是说明每一层应该做什么。然而，ISO还是对各层制定了标准，每一层都是作为一个单独的国际标准来颁布的。

(2)TCP/IP参考模型

TCP/IP参考模型是一种传输协议，提供了许多不同的网络服务。

TCP/IP协议组由TCP（传输控制协议）和IP（网际协议）两部分组成。TCP表明是处于传输层，IP意为是在网络层。在传输层上面是应用层。应用层包括所有高层协议。早期的协议包括虚拟终端TELNET、文件传送协议FTP、电子邮件SMTP和域名服务DNS。

现在我们知道，TCP/IP协议是因特网的基础。这些协议在用户们的支持下不断地改变和进化着。

Text 3 Local Area Network

A LAN (Local area data network) is a group of computers. The work devices connected together usually within the same building. By definition, the connections must be high-speed and relatively inexpensive (e.g. token ring or Ethernet). For example, a LAN may be used to interconnect workstations distributed around offices within a single building or a group of buildings such as a university campus.

LANs consist of carefully selected groups of components (hardware and software). They are configured for the specific requirements of the organization. A LAN is generally limited to the size of a department or an organization. And a LAN often consists of 2 to 100 devices. LANs usually contain resources such as servers, printers, and connections to other networks through internetworking devices. The internetworking devices include switches and routers.

随意编辑

精品文档

In the next section we will discuss the structure of the different types of LAN.

(1)Topology

Most wide area networks, such as the PSTN, use a mesh (sometimes referred to as a network) topology.With LANs, however, the limited physical separation of the subscriber DTEs allows simpler topologies to be used. The four topologies in common use are star, bus, ring and hub.

The most widespread topology for LANs designed to function as data communication subnetworks for the interconnection of local computer-based equipment is the hub topology. It is a variation of the bus and ring.

(2)Transmission media

Twisted pair, coaxial cable and optical fibre are the three main types of transmission medium used for LANs.

(3)Medium access control methods

Two techniques have been adopted for use of the medium access control in the LANs. One is carrier-sense-multiple-access with collision detection, and the other is control token.

参考译文

局域网

局域数据网(局域网)由若干计算机组成。通常是一幢楼内的工作设备被连接在一起。通过定义可知，这种连接一定是高速并且相对廉价的（如：令牌网和以太网）。例如，一个局域网可以把一幢楼里或像大学校园内楼群里的各个办公室的工作站连在一起。

局域网是由精心挑选的各组设备（硬件和软件）构成的。它们根据组织的各种特殊需要

随意编辑

精品文档

来配置。局域网的大小一般限制在一个部门或者一个组织，由2～100台电脑组成。局域网经常包含一些资源，如一些服务器和打印机，而且可以通过网络设备与其他的网络连接。这些网络设备包括交换机和路由器等。

接下来，我们将讨论不同类型局域网的结构。

(1)拓扑结构

大多数广域网，如公共电话交换网（PSTN），使用网状（有时称为网络）拓扑结构；而局域网由于用户数据终端设备相距很近，可采用简单的拓扑结构。常用的有星形、总线、环形和集线器等4种拓扑结构。

应用最广的、用于互连本部门计算机设备以进行数据通信的局域网拓扑结构是集线器拓扑结构。这种拓扑结构是总线和环形拓扑结构的变种。

(2)传输媒体

双绞线、同轴电缆和光纤是局域网采用的3种主要传输媒体。

(3)媒体访问控制方法

局域网中采用了两种媒体访问控制技术，一种是载波侦听多路访问／冲突检测技术（CSMA/CD），另一种是令牌控制技术。

Text 4 Internet

The Internet is used by millions of people across the world to communicate business and personal information. The Internet is huge. Then we will talk about the difference of “an internet”and “ the Internet”.

An internet (note the lower case "i") is a computer network. It allows computers with distinctive software and hardware to communicate. Many kinds of computers can be connected to an internet. Each computer can serve a specialized

随意编辑

本文来源：https://www.bwwdw.com/article/hnnq.html