信息网络通信基础.ppt

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1、Data Communications&NetworkingChapter 1Introduction第一章第一章 绪论绪论Department of Electronic and Communication EngineeringNCEPU1Data Communications&Networking2Data Communications&Networking3Data Communications&Networking4Data Communications&NetworkingChapter 1Introduction绪论绪论5Data Communications&Networkin

2、g1-1 DATA COMMUNICATIONS 数据通信数据通信The The term term telecommunicationtelecommunication means means communication communication at at a a distance.distance.The The word word datadata refers refers to to information information presented presented in in whatever whatever form form is is agreed agreed u

3、pon upon by by the the parties parties creating creating and and using using the the data.data.Data Data communicationscommunications are are the the exchange exchange of of data data between between two two devices devices via via some some form form of of transmission medium such as a wire cable.t

4、ransmission medium such as a wire cable.Components 组成组成Data Representation 数据表示数据表示Data Flow 数据流数据流Topics discussed in this section:Topics discussed in this section:6Data Communications&Networking Data communications are the exchange of data between two devices via some form of transmission medium s

5、uch as a wire cable.The effectiveness of a data communications system depends on four fundamental characteristics:1.Delivery.传递性 The system must deliver data to the correct destination2.Accuracy.准确性3.Timeliness.及时性4.Jitter.抖动性 Jitter refers to the variation in the packet arrival time.(audio or video

6、)7Data Communications&NetworkingFigure 1.1 Five components of data communication1.Message 报文报文 2.Sender 发送方发送方 3.Receiver 接受方接受方 4.Medium 介质介质5.Protocol 协议协议8Data Communications&NetworkingData Representation Data Representation 数据表示数据表示数据表示数据表示 Text 文本 Numbers 数字 Images 图像 Audio 音频 Video 视频9Data Com

7、munications&NetworkingFigure 1.2 Data flow(simplex,half-duplex,and full-duplex)p6 数据流分为单工、半双工和双工数据流分为单工、半双工和双工10Data Communications&Networking1-2 NETWORKS 网络网络A A networknetwork is is a a set set of of devices devices(often(often referred referred to to as as nodesnodes)connected connected by by com

8、munication communication linkslinks.A A node node can can be be a a computer,computer,printer,printer,or or any any other other device device capable capable of of sending sending and/or and/or receiving receiving data data generated generated by by other other nodes nodes on on the the work.网络是指由介质

9、链路连接在一起的一系列设备（常常被称为网络节点）Distributed Processing 分布式处理分布式处理Network Criteria 网络准则网络准则Physical Structures物理结构物理结构Network Models网络模型网络模型Categories of Networks网络分类网络分类Interconnection of Networks:Internetwork网络互联：因特网网络互联：因特网Topics discussed in this section:Topics discussed in this section:11Data Communicat

10、ions&Networking1.2.11.2.1 Distributed processing Distributed processing分布式处理分布式处理分布式处理分布式处理Advantages:1.Security/encapsulation 安全性安全性/封装性封装性2.Distributed databases 分布式数据库分布式数据库3.Faster problem solving 更快的解决问题方式更快的解决问题方式4.Security through redundancy 通过冗余达到通过冗余达到安全性安全性5.Collaborative processing 协作处理协作

11、处理12Data Communications&Networking 安全性安全性网络准则网络准则可靠性可靠性性能性能性能：多种形式衡量，包括传输时间和响应时间。性能取决于多种因素用户数量、传输介质类型、所连接的硬件能力以及软件效率可靠性：出现故障的频率、一条链路从故障恢复所花费的时间可靠性：保护数据免受未授权的访问1.2.2 1.2.2 Network Criteria Network Criteria 网网网网络络准准准准则则 13Data Communications&NetworkingFigure 1.3 Types of connections:point-to-point and

12、 multipoint点到点点到点和多点和多点Reserved capacity VS Shared capacity连接类型1.2.3 1.2.3 物理结构物理结构 Physical Structures14Data Communications&NetworkingFigure 1.4 Categories of topology物理拓扑结构15Data Communications&NetworkingFigure 1.5 A fully connected mesh topology(five devices)优点:1.专用线路dedicated links2.健壮性 robust3.

13、秘密性、安全性privacy/security4.故障识别、排除fault identification/isolation5.缺点：6.安装复杂，费用离谱16Data Communications&NetworkingnExample The Lucky Ducky Corporation has a fully connected mesh network consisting of eight devices.Calculate the total number or cable links needed and the number of ports for each devices.

14、nSolution Number of links=n(n-1)/2=8(8-1)/2=28 Number of ports per device =n-1=8-1=717Data Communications&NetworkingFigure 1.6 A star topology connecting four stationsA dedicated point-to-point link only to a central controller,hub星型拓扑用于局域网中，高速局域网通常用星型拓扑结构18Data Communications&NetworkingFigure 1.7 A

15、 bus topology connecting three stationsUsed in early Ethernet LANs but they are less pupular now.总线拓扑是多点配置的(multipoint)。Ease of installation;less cabling;易安装，使用电缆最少，主缆能支持的抽头数和抽头之间的距离都有限制，在各个抽头处的信号反射会降低传输质量。健壮性差(robustness)引出线引出线分接头分接头19Data Communications&NetworkingFigure 1.8 A ring topology connect

16、ing six stations被IBM引入令牌环局域网时曾盛行一时，目前要求高速局域网，这种拓扑结构就不流行了。Example 1.2If the devices in Example 1.1 are configured as a ring instead of a mesh,how many cable links are required.20Data Communications&NetworkingFigure 1.9 A hybrid topology混合混合:a star backbone with three bus networks21Data Communications

17、&Networking1.2.41.2.4 Network Models 网络模型OSI 7-layer modelInternet 5-layer model1.2.51.2.5 Categories of Networks 网络分类Local Area Network 局域网Wide Area Network 广域网Metropolitan Area Network 城域网Interconnection of Networks:Internetwork网络互联：因特网22Data Communications&NetworkingFigure 1.10 An isolated LAN co

18、nnecting 12 computers to a hub in a closet房间房间Currently,LAN size is limited to a few kilometers.Common LAN topologies:bus,ring,and star.Speeds are normally 100 or 1000 Mbps,wireless LANs23Data Communications&NetworkingFigure 1.11 WANs:a switched WAN and a point-to-point WANWAN:X.25;ATM24Data Communi

19、cations&Networking1.12 A heterogeneous network made of four WANs and two LANsInternetworkheterogeneous不同种类的不同种类的25Data Communications&Networking1-3 THE INTERNET因特网因特网The The InternetInternet has has revolutionizedrevolutionized彻彻彻彻底底底底改改改改变变变变 many many aspects aspects of of our our daily daily live

20、s.lives.It It has has affected affected the the way way we we do do business business as as well well as as the the way way we we spend spend our our leisure leisure time.time.The The Internet Internet is is a a communication communication system system that that has has brought brought a a wealth w

21、ealth ofof information information to our fingertipsto our fingertips and organized it for our use.and organized it for our use.A Brief History 历史简介历史简介The Internet Today(ISPs)因特网现状（因特网服务提供商）因特网现状（因特网服务提供商）Topics discussed in this section:Topics discussed in this section:26Data Communications&Networ

22、kingARPAARPA：Advanced Research Projects Agency Advanced Research Projects Agency(美国国防部美国国防部美国国防部美国国防部)高级计划研究署高级计划研究署高级计划研究署高级计划研究署7070年代初的美国深陷在越南战场的泥潭中，不能自拔，而国年代初的美国深陷在越南战场的泥潭中，不能自拔，而国内的反战呼声一浪高过一浪。美国到了二战后第一个内外交困的内的反战呼声一浪高过一浪。美国到了二战后第一个内外交困的年代。虽然这样，但是国内的各种科学技术还是在飞速地发展。年代。虽然这样，但是国内的各种科学技术还是在飞速地发展。ARPA

23、NETARPANET在不断地壮大。在不断地壮大。19701970年的年的ARPANETARPANET已初具雏形，并且开始向非军用部门开放，已初具雏形，并且开始向非军用部门开放，许多大学和商业部门开始接入。但是它只有四台主机联网运行，许多大学和商业部门开始接入。但是它只有四台主机联网运行，甚至连局域网（甚至连局域网（LANLAN）的技术也还没有出现。当时用作接口机的）的技术也还没有出现。当时用作接口机的Honeywell DDP516Honeywell DDP516型小型机的内存只有型小型机的内存只有12K12K。ARPANETARPANET在洛杉矶的加利福尼亚大学洛杉矶分校、加州大学在洛杉矶的

24、加利福尼亚大学洛杉矶分校、加州大学圣巴巴拉分校、斯坦福大学、犹他州大学四所大学的圣巴巴拉分校、斯坦福大学、犹他州大学四所大学的4 4台大型计台大型计算机采用分组交换技术，通过专门的接口信号处理机（算机采用分组交换技术，通过专门的接口信号处理机（IMPIMP：interface message processorinterface message processor）和专门的通信线路相互连接。）和专门的通信线路相互连接。为了把这四个不同型号、使用不同操作系统、不同数据格式、不为了把这四个不同型号、使用不同操作系统、不同数据格式、不同终端的计算机连在一起实现相互通信和资源共享，有许许多多同终端的计

25、算机连在一起实现相互通信和资源共享，有许许多多的人为此煞费苦心、艰辛探索，付出了无数的心血。其中包括有的人为此煞费苦心、艰辛探索，付出了无数的心血。其中包括有“阿帕网阿帕网”之父的之父的拉里拉里罗伯茨罗伯茨。(信息技术处处长信息技术处处长-鲍勃鲍勃 泰勒泰勒,ARPA署长-赫兹菲尔德)27Data Communications&NetworkingARPANETARPANET：最初，最初，ARPAnetARPAnet主要是用于军事研究目的，主要是用于军事研究目的，它主要是基于这样的指导思想：网络必须经受得住故障的它主要是基于这样的指导思想：网络必须经受得住故障的考验而维持正常的工作，一旦发生战

26、争，当网络的某一部考验而维持正常的工作，一旦发生战争，当网络的某一部分因遭受攻击而失去工作能力时，网络的其他部分应能维分因遭受攻击而失去工作能力时，网络的其他部分应能维持正常的通信工作。持正常的通信工作。ARPAnetARPAnet在技术上的另一个重大贡献是在技术上的另一个重大贡献是TCP/IPTCP/IP协议簇的开发和利用。作为协议簇的开发和利用。作为InternetInternet的早期骨干网，的早期骨干网，ARPAnetARPAnet的试验并奠定了的试验并奠定了InternetInternet存在和发展的基础，较好存在和发展的基础，较好地解决了异种机网络互联的一系列理论和技术问题。地解决

27、了异种机网络互联的一系列理论和技术问题。19831983年，年，ARPAnetARPAnet分裂为两部分，分裂为两部分，ARPAnetARPAnet和纯军事用的和纯军事用的MILNETMILNET。同时，局域网和广域网的产生和逢勃发展对同时，局域网和广域网的产生和逢勃发展对InternetInternet的进的进一步发展起了重要的作用。一步发展起了重要的作用。ARPANETARPANET另一项好处是，资讯高另一项好处是，资讯高速公路使得全世界的速公路使得全世界的hackershackers能聚在一起，不再像以前孤立能聚在一起，不再像以前孤立在各地形成一股股的短命文化，网络把他们汇流成一股强在各

28、地形成一股股的短命文化，网络把他们汇流成一股强大力量。大力量。28Data Communications&NetworkingChronology of Internet Evolutionn1966:ARPA packet switching experimentationn1969:1st ARPANET nodes operationaln1972:Distributed email invented(1st killer application:75%of traffic)n1973:1st non-US computer linked to ARPANETn1975:ARPANET

29、transitioned to Defense Communications Agencyn1980:TCP/IP experimentation beginsn1981:New host added every 20 daysn1983:TCP/IP switchover completen1986:NSFnet backbone createdn1990:ARPANET retiredn1991:Gopher introducedn1991:WWW introducedn1991:PGP releasedn1992:Mosaic inventedn1995:Internet backbon

30、e privatizedn1996:OC-3(155Mbps)backbone builtn1998:Number of registered domain names exceed 2 millionn2000:Number of index able web pages exceed 1 billion29Data Communications&NetworkingFigure 1.13 Hierarchical organization of the InternetISP：Internet Service Provider30Data Communications&Networking

31、1-4 PROTOCOLS AND STANDARDS 协议和标准协议和标准协议和标准协议和标准In In this this section,section,we we define define two two widely widely used used terms:terms:protocolsprotocols and and standardsstandards.First,First,we we define define protocol,protocol,which which is is synonymous synonymous withwith rule.rule.T

32、hen Then we we discuss discuss standards,standards,which which are are agreed-uponagreed-upon rules.rules.Protocols协议协议Standards标准标准Standards Organizations 标准化组织标准化组织Internet Standards 因特网标准因特网标准Topics discussed in this section:Topics discussed in this section:31Data Communications&NetworkingPerform

33、ance Number of usersType of transmission mediumHardware Software Reliability Frequency of failure 故障频率故障频率Recovery time of a network after a failure 网络故障恢复时间网络故障恢复时间Catastrophe 灾难性事故灾难性事故Security Unauthorized access 未授权访问未授权访问Viruses 病毒病毒32In data communication,a protocol is a set of rules(conventio

34、ns)that govern all aspects of information communicationNote:在数据通信中在数据通信中,协议是指一组用来控制信息通信协议是指一组用来控制信息通信的各个方面的规则的各个方面的规则(约定约定)33Data Communications&NetworkingStandards OrganizationsStandards Creation Committees 标准化组织Forums 论坛：quickly test,evaluate,and standardize new technologies.Regulatory Agencies 管理

35、机构34Data Communications&NetworkingStandards Creation Committees 标准化组织nISO 国际标准化组织nITU-T（International Telecommunication Union Telecommunication Standards Sector）国际电信联盟电信标准化部nANSI（American National Standards Institute）美国国家标准化协会nIEEE(Institute of Electrical and Electronics Engineers)电气电子工程师协会nEIA(Elec

36、tronic Industries Association)电子工业协会 standards for physical connection interfaces and electronic signaling nTelcordiaBellcore 贝尔中心Regulatory AgenciesFCC(Federal Communications Commission)美国联邦通信委员会 authority over interstate and international commerce in the communications field Internet StandardsRFC(Request for Comment)Internet标准草案35