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Network architecture describes how computer network is arranged and how computer resources are shared.
There are a number of specialized terms that describe computer network. Some terms often used with networks are: node, client, server, network operating system, distributed processing and host computer.
A node is any device that is connected to a network. It could be a computer, printer, or communication or data storage device.
A client is a node that requests and uses resources available from other nodes. Typically, a client is a user's microcomputer.
A server is a node that shares resources with other nodes. Depending on the resources shared, it may be called a file server, printer server, communication server, or database server.
Network operating system likes Windows, it controls and coordinates the activities between computers on a network. These activities include electronic communication, information, and resource sharing.
In a distributed processing system, computing power is located and shared at different locations. [1] This type of system is common in decentralized organizations where divisional offices have their own computer systems. The computer systems in the divisional offices are networked to the organization's main or centralized computer.
Host computer is a large centralized computer, usually a minicomputer or a mainframe.
A network may consist only of microcomputers, or it may integrate microcomputers or other devices with large computers. [2] Networks can be controlled by all nodes working together equally or by specialized nodes coordinating and supplying all resources. Networks may be simple or complex, self-contained or dispersed over a large geographical area.
Configuration A network can be arranged or configured in several different ways. The four principal configurations are star, bus, ring, and hierarchical.
In a star network, a number of small computers or peripheral devices are linked to a central unit. This central unit may be a host computer or a file server. All communications pass through this central unit. Control is maintained by polling. That is, each connecting device is asked whether it has a message to send. Each device is then in turn allowed to send its message. One particular advantage of the star form of network is that it can be used to provide a time-sharing system. That is, several users can share resources ("time") on a central computer. The star is a common arrangement for linking several microcomputers to a mainframe that allows access to an organization's database.
In a bus network, each device in the network handles its own communications control. There is no host computer. All communications travel along a common connecting cable called a bus. As the information passes along the bus, it's examined by each device to see if the information is intended for it. The bus network is typically used when only a few microcomputers are to be linked together. This arrangement is common in systems for electronic mail or for sharing data stored on different microcomputers. The bus network is not as efficient as the star network for sharing common resources. (This is because the bus network is not a direct link to the resource.) However, a bus network is less expensive and is in very common use.
In a ring network, each device is connected to two other devices, forming a ring. There is no central file server or computer. Messages are passed around the ring until they reach the correct destination. With microcomputers, the ring arrangement is the least frequently used of the four networks. However, it is often used to link mainframes, especially over wide geographical areas. These mainframes tend to operate fairly autonomously. They perform most or all of their own processing and only occasionally share data and programs with other mainframes. A ring network is useful in a decentralized organization because it makes possible a distributed data processing system. That is, computers can perform processing tasks at their own dispersed locations. However, they can also share programs, data and other resources with each other.
The hierarchical network consists of several computers linked to a central host computer, just like a star network. However, these other computers are also hosts to other, smaller computers or to peripheral devices. Thus, the host at the top of the hierarchy could be a mainframe. The computers below the mainframe could be minicomputers, and those below, microcomputers. The hierarchical network—also called a hybrid network—allows various computers to share databases, processing power, and different output devices. A hierarchical network is useful in centralized organizations. For example, different departments within an organization may have individual microcomputers connected to departmental minicomputers. The minicomputers in turn may be connected to the corporation's mainframe, which contains data and programs accessible to all.
Strategies Every network has a strategy or way of coordinating the sharing of information and resources. The most common network strategies are peer-to-peer and client/server systems.
In a peer-to-peer network system nodes can act as both servers and clients. For example, one microcomputer can obtain files located on another microcomputer and can also provide files to other microcomputers. A typical configuration for a peer-to-peer system is the bus network. Commonly used net operating systems are Apple's Macintosh Peer-to-Peer LANs, Novell's Netware Lite, and Microsoft's Windows for Workgroups. There are several advantages to using this type of strategy. The networks are inexpensive and easy to install, and they usually work well for smaller systems with less than ten nodes. As the number of nodes increases, however, the performance of the network declines. Another disadvantage is the lack of powerful management software to effectively monitor a large network's activities. For these reasons, peer-to-peer network are typically used by small networks.
Client/server network systems use one powerful computer to coordinate and supply services to all other nodes on the network. This strategy is based on specialization. Server nodes coordinate and supply specialized services, and client nodes request the services. Commonly used net operating systems are Novell's Netware, Microsoft's LAN and Windows NT. One advantage of client/server network systems is their ability to handle very large networks efficiently. Another advantage is the powerful network management software that monitors and controls the network's activities. The major disadvantages are the cost of installation and maintenance.
Words
| autonomously | adv. | 自主地 |
| centralized | adj. | 集中的，中央集权的 |
| destination | n. | 目的地，目标 |
| decentralized | adj. | 分散（型）的 |
| dispersed | adj. | 分散的，漫布的，细分的 |
| divisional | adj. | 分开的 |
| evolve | v. | 进化，开展 |
| hierarchical | adj. | 分层的 |
| hose | n. | 软管 |
| v. | 接以软管 | |
| integrate | v. | 使……结合，使…完整 |
| maintenance | n. | 维护，保持，保养 |
| node | n. | 节点，分支 |
| polling | n. | 轮询，探询，查询 |
| self-contained | adj. | 独立的，配套的 |
| specialization | n. | 专门，专业化 |
| strategy | n. | 战略 |
Phrases
| distributed processing system | 分布式处理系统 |
| file server | 文件服务器 |
| host computer | 主机 |
| in turn | 轮流，依次 |
| peer-to-peer | 对等，对等网络 |
| resource sharing | 资源共享 |
| time sharing | 分时 |
Notes
［1］ 例句：This type of system is common in decentralized organizations where divisional offices have their own computer systems。
分析：句中where引导的是定语从句，用来修饰organizations。
译文：这类系统在分散型机构中很常见，其分开的办公室具有它们自己的计算机系统。
［2］ 例句：Networks can be controlled by all nodes working together equally or by specialized nodes coordinating and supplying all resources.
分析：分词短语working together equally作定语修饰all nodes，分词短语coordinating and supplying all resources作定语修饰specialized nodes。
译文：网络可以由一起平等工作的所有节点来控制，或者是由协调和提供所有资源的专用节点控制。
Exercises
Ⅰ. Put "true" or "false" in the brackets for the following statements according to the passage.
1. ( ) The network architecture describes how a computer network is arranged; the arrangement is called topology.
2. ( ) In a distributed processing system, computing power is located and shared at the same location.
3. ( ) In a star network, each device can require to send message simultaneously.
4. ( ) In a bus network, as information passes through the bus, every node can receive it.
5. ( ) With microcomputers, the ring arrangement is the most frequently used of the four networks.
6. ( ) A hierarchical network is useful in distributed organizations.
7. ( ) In a peer-to-peer network system nodes can act as both servers and clients, that is, the nods can exchange their roles.
8. ( ) In a client/server system, all nodes on the network have equal responsibilities for coordinating the network's activities.
9. ( ) The client/server system has powerful network management software.
10. ( ) One organization can only have one network configuration.
Ⅱ. Fill in the blanks according to the passage.
1. Network architecture describes how computer network isand how computer resources are.
2. Ais any device that is connected to a network.
3. Network operating systemandelectronic communication, information, and resource sharing.
4. In a star network, control is maintained by.
5. In a ring network, each device is connected to two other devices, forming a.
6. A ring network is useful in aorganization because it makes possible a data processing system.
7.network systems use one powerful computer to coordinate and supply services to all other nodes on the network.
8. The most common network strategies areand client/server systems.
9. Every network has aor way of coordinating the sharing of information and resources.
10. The hierarchical network consists of several computers linked to a host computer, just like a star network.
Ⅲ. Translate the following words and expressions into Chinese.
1. distributed processing system
2. network architecture
3. peer-to-peer system
4. strategy
5. hierarchical network
6. host computer
7. peripheral device
8. decentralized organization
9. self-contained
10. configuration
This section consists of brief entries, showing the year of an event, a comment regarding the event and the personalities, as appropriate.
1969: The first four nodes of the ARPANET are deployed. In order, they come up at UCLA, SRI, university of California at Santa Barbara, and the University of Utah.
1972: Ray Tomlinson of BBN introduces network email and the @ sign.
1972: Norm Abramson's Alohanet connected to the ARPANET. This eventually led to the Packet Radio Net (PRNET) and was the first additional network connected to the ARPANET.
1973: Motivated by the three interconnected networks, Bob Kahn and Vint Cerf conceive of the Transmission Control Protocol (TCP) and publish the idea formally in 1974. This architecture would allow packet networks of different kinds to interconnect and machines to communicate across interconnected networks.
1977: TCP is used to connect three networks (ARPANET, PRNET, and SATNET) in an intercontinental demonstration.
1979: CSNET is conceived as a result of a meeting convened by Larry Landweber. The National Science Foundation (NSF) funds it in early 1981. This enabled the connection of many more computer science researchers to the growing Internet.
1980: Ethernet goes commercial through 3-Com and other vendors.
1981: IBM introduces their first personal computer (PC).
1983: TCP/IP becomes the official standard for the ARPANET.
1984: The Domain Name System (DNS) is designed by Paul Mockapetris.
1988: Robert Morris unleashes the first Internet worm. This is the commencement of the dark side of the Internet.
1989: Tim Berners-Lee proposes a global hypertext project, to be known as the World Wide Web (WWW).
1989: ARPANET backbone replaced by NSFNET.
1991: Tim Berners-Lee makes the first Web site available on the Internet.
1992: Internet Society is formed.
1993: The Mosaic browser is released by Marc Andreessen and Eric Bina of the National Center for Supercomputer Applications (NCSA) at the University of Illinois, Urbana-Champaign.
1994: Netscape browser is released.
1995: Bill Gates issues "The Internet Tidal Wave" memo within Microsoft.
1996: In the United States, more email is sent than postal mail.
1998: Blogs begin to appear.
1998: Voice over IP (VoIP) equipment begins rolling out.
2001: English is no longer the language of the majority of Internet users. It falls to a 45 percent share.
2002: Broadband users exceed the number of dial-up users in the United States.
2005: 812 million cell phones sold; 219 million laptop computers sold.
2005: Google is the darling of the Internet.
2005: Peer-to-peer networks grow.
2005: Google Maps and Google Earth appear.
2005: Web 2.0 technologies heat up.
2007: Mobile TV ads, applications, and content emerging.
2007: Apple introduces the iPhone.
2007: Google lays out Android, its open cell phone platform.
It is clear that the Internet is a vital force and has grown considerably over its lifetime.
Words
| unleash | v. | 释放 |
| commencement | n. | 开始，毕业典礼 |
| tidal | adj. | 潮汐的，定时涨落的 |
| postal | adj. | 邮政的，邮局的 |
| vital | adj. | 重大的，生机的，至关重要的 |
| lifetime | n. | 一生，终生，寿命 |
| entry | n. | 登录，条目，进入，入口 |
| personality | n. | 个性，人格，名人 |
| appropriate | adj. | 适当的 |
Abbreviations
UCLA (University of California at Los Angeles) （美国）加利福尼亚大学洛杉矶分校
网络体系结构描述计算机网络是如何连接以及计算机资源是如何共享的。
描述计算机网络的专业术语很多，经常用于描述的有：节点、客户机、服务器、网络操作系统、分布处理及主计算机。
节点是连接到网络的任一设备，它可以是计算机、打印机、通信或数据存储设备。
客户机是请求和使用其他节点资源的节点。通常情况下，客户机就是用户的微机。
服务器是和其他节点共享资源的节点。根据所共享的资源不同，服务器可以被称为文件服务器、打印机服务器、通信服务器或数据库服务器。
网络操作系统像Windows，它控制和协调网络中计算机间的活动。这些活动包括电子通信、信息以及资源共享。
在分布式处理系统中，计算能力被分布在不同的地方共享。这类系统在分散型机构中很常见，其分开的办公室具有它们自己的计算机系统。这些分开的办公室的计算机系统联网到该机构的主计算机或中央计算机。
主计算机是大的中央计算机，通常是小型机或大型机。
网络可以仅由微机组成，也可以由微机或其他设备与较大计算机结合而来。网络可以由一起平等工作的所有节点来控制，或者是由协调和提供所有资源的专用节点控制。网络可以是简单的，也可以是复杂的；可以是独立的，也可以是分散在大的地理区域内的。
结构 网络可以用几种不同的方式排列或连接。主要的结构有四种：星型、总线型、环型和层次型。
在星型网络中，一些小的计算机或外部设备被连接到一个中心设备。这个中心设备可以是主计算机或文件服务器，所有的通信都通过这个中心设备。控制是由轮询实现的。也就是说，每一个连接的设备都被询问是否有信息发送，然后每个设备被轮流允许发送其信息。星型网络最大的优点是它能用于提供分时系统，即几个用户可以在一个中心计算机上共享资源（“时间”）。在将几个微机连接到大型机上以访问一个机构的数据库时，经常使用星型结构排列。
在总线型网络中，网络中的每一个设备处理自己的通信控制，该网络中没有主计算机。所有通信沿着被称为总线的公共连接电缆传输。信息通过总线时，由每一个设备检验以判定该信息是否是给自己的。当只有几个微机需要连接在一起时，一般使用总线型网络。这种结构常见于发送电子邮件或共享存储在不同微机上的数据的系统。对于共享资源，总线型网络没有星型网络的效率高（这是因为总线型网络不是直接连接到资源上的）。然而，总线型网络成本不高而且很常用。
在环型网络中，每一个设备被连接到其他两个设备形成环路。环型网络中没有中央文件服务器或中央计算机，信息通过环路直至到达正确的目的地。对于微型机来讲，环型结构是这四种网络当中使用最少的。然而环型网经常被用于连接大型机，尤其是在跨度很大的地理区域。这些大型机趋于非常自主的运作，它们完成自己绝大多数或全部的处理任务，偶尔与其他大型机共享数据和程序。环型网络在分散型机构中很有用，因为这使得分布式数据处理系统成为可能，即计算机在它们自己分散的位置就可以完成处理任务。然而，它们也可以相互共享程序、数据以及其他的资源。
层次型网络是由几个连接到中心计算机的计算机构成的，就像星型网络。然而，这些计算机又可以作为其他更小的计算机或外部设备的主机。这样，在层次顶部的主计算机就可能是大型机，在大型机下层的可能是小型机，小型机下层是微机。层次型网络（也被称为混合型网络）允许各种计算机共享数据库、处理能力及不同的输出设备。层次型网络适合于集中的机构。例如，一个机构内部的不同部门可以有连接到部门小型机上的单个微机，这个小型机依次可以连接到公司的大型机，公司大型机包含所有机器可以访问的程序和数据。
策略 每一个网络都有协调信息和资源的策略或方法，最常用的网络策略是对等和客户／服务器系统。
在对等网络系统中，节点既可以是服务器也可以是客户机。例如，一个微机可以获得位于另一个微机上的文件，也一可以给其他的微机提供文件。对等系统的典型结构是总线型网络。常用的网络操作系统有Apple公司的Macintosh Peer-to-Peer LANS、Novell公司的Netware Lite和Microsoft公司的Windows for Workgroups。使用这类策略有几个优点。这种网络不贵且易于安装，通常在节点数小于10个的小系统中能较好地工作。然而，当节点的数目增加时，网络的性能就会下降。缺点是缺乏强大的管理软件，以有效地监控大的网络活动。由于这些原因，对等网络一般用于小型网络中。
客户／服务器网络系统使用一台功能强大的计算机来协调网络上的其他节点，并提供服务。这一策略是基于专业化的，服务器节点协调和提供专门的服务，客户节点请求服务。常用的网络操作系统有：Novell公司的Netware、Microsoft公司的LAN和Windows NT。客户／服务器网络系统的优点是能够有效地处理大的网络活动，同时它还有强有力的网络管理软件监视和控制网络活动。其缺点是安装和维护的费用较高。
本部分是一些简单条目，包括事件的年份、关于事件的注释以及人物。
1969：具有4个节点的ARPANET装备好了，分别位于加利福尼亚大学洛杉矶分校（UCLA）、SRI、加利福尼亚大学圣迭戈分校（UCSB）和犹他大学。
1972：BBN的Ray Tomlinson引入网络电子邮件和＠符号。
1972：Norm Abramson的Alohanet连接到ARPANET（阿帕网），成为第一个连接到阿帕网的其他网络，这最终促使了分组无线网（PRNET）的形成。
1973：由三个互联网络推动，Bob Kahn和Vint Cerf提出传输控制协议（TCP）并于1974年正式公布。这种架构允许不同类型的包交换网络互连，机器能通过互连的网络进行通信。
1977：TCP被用于连接洲际示范的三个网络（阿帕网ARPANET、分组无线网PRNET和卫星通信网SATNET）。
1979：CSNET被认为是在Larry Landweber主持召开的一次会议上构思出来的。1981年初得到美国国家科学基金会（NSF）的资助，使得更多的计算机科学研究人员可以连接到互联网。
1980：以太网通过3-COM和其他厂商进入商业市场。
1981：IBM公司推出了他们的第一台个人计算机（PC）。
1983：TCP/IP协议成为阿帕网（ARPANET）的正式标准。
1984：Paul Mockapetris提出域名系统（DNS）。
1988：Robert Morris释放第一个互联网蠕虫病毒，这是互联网黑暗面的开始。
1989：Tim Berners-Lee提出了被称为万维网（WWW）的全球超文本项目。
1989：阿帕网（ARPANET）的骨干作用被NSFNET取代。
1991：Tim Berners-Lee建成了互联网上的第一个网站。
1992：互联网协会成立。
1993：国家超级计算机应用中心（NCSA）的Marc Andreessen和Eric Bina在伊利诺斯大学Urbana-Champaign分校发布了Mosaic浏览器。
1994：Netscape浏览器发布。
1995：比尔·盖茨在微软发表了“互联网浪潮”备忘录。
1996：在美国，电子邮件发送量超过邮寄的邮件。
1998：博客开始出现。
1998：网络电话（VoIP）设备开始推出。
2001：英语已经不再是大多数互联网用户的语言，下降到45％的份额。
2002：在美国宽带用户的数量超过拨号上网用户的数量。
2005：手机销量达8.12亿部；笔记本电脑销量达2.19亿。
2005：谷歌成为互联网的宠儿。
2005：点对点网络增长。
2005：Google Maps和Google Earth出现。
2005：Web 2.0技术升温。
2007：移动电视广告、应用和内容出现。
2007：苹果公司推出iPhone。
2007：谷歌投资开放式手机平台Android。
显然，互联网是一个重要力量，从出现以来已经显著成长。