数据通信基础：第1章 课程简介

1、数据通信基础第1章 (课程简介)20120227BitLiuJKPage 2 本课程信息课程名称：数据通信基础课程定位：面向信息与电子学院的专业基础课先修课程：信号与系统后续课程：计算机网络、现代通信系统、数字通信网、数字通信原理这是第一次开设数据通信的课程，主要目的是强调数据通信在现代通信技术中的重要性，以便区别于计算机网络类的课程。现代通信已经不是传统意义下的以电话通信为主的电子通信，而是逐渐转变为通信与网络的紧密结合。今天的移动互联网就是一个明显的例子。20120227BitLiuJKPage 3 课程概要总共32学时 (包含2学时期末考试)平时有作业和小测验希望通过网络提交作业随堂不定

2、期的抽查小测验期末有闭卷考试期末 75% + 平时 25% = 课程总成绩 100%20120227BitLiuJKPage 4 课程的目的“课程的目的是要使学生理解数字通信网络的基本原理，特别强调物理层的重要性。”能够理解数据通信的 基本概念能够描述 通信网络的原理20120227BitLiuJKPage 5 参考书Textbook: Forouzan, B.A. (2003). Data Communications and Networking, 3rd ed. McGraw-Hill, 原版书，第4版英文版由机械工业出版社影印出版, 2007年Tannenbaum, A.S. (200

3、3). Computer Networks, 4th ed. Prentice Hall.Stallings, W. (2004). Data and Computer Communications, 7th ed. Prentice Hall.中文参考书高传善等，数据通信与计算机网络（第2版），2004年，高等教育出版社谢希仁，计算机网络（第5版），2007年，电子工业出版社崔良海等，数据通信技术教程，2009年，北京大学出版社达新宇等，数据通信原理与技术（第2版），2010年，电子工业出版社Jerry Fitzgerald等著，邓劲生等译，数据通信与网络技术大学教程（第9版），2008年，

4、清华大学出版社20120227BitLiuJKPage 6 20120227BitLiuJKPage 7 教材的网站基于教材“Data Communications and Networking” (第3版) 作者 B.A. Forouzan 出版社 McGraw-Hill教材的网址: /forouzan在线学习中心包括的内容 PPT，奇数题目的解答，每一章的测验题。本课程主要讲解的章节（暂定）Ch1 IntroductionCh2 Network ModelsCh3 SignalsCh4 Digital TransmissionCh7 Transmission MediaCh10 Error

5、 Detection Ch11 Data LinkCh14 LAN20120227BitLiuJKPage 8 Ch15 WLANCh19 AddressingCh20 Network LayerCh22 UDP and TCPCh27 HTTP and WWW20120227BitLiuJKPage 9 内容简介第1章 课程简介1.1 数据通信1.2 网络1.3 因特网1.4 协议与标准1.5 标准化组织20120227BitLiuJKPage 10 数据通信基本知识定义电信 Define Telecommunications定义数据通信 Define Data Communications

6、理解数据通信的需求 Understand the data communications Requirements列举各种网络拓扑结构 List different network topologies理解通信网络的发展历史 Understand the evolution of communications network20120227BitLiuJKPage 11 数据通信与网络技本概念“Communications通信” by definition refers to the transfer (convey) of information from one place to anot

7、her between two individuals using agreed symbols, signs or even human behavior.Talking to your friend over a phoneWriting a mail to overseas relativeLecturing a course20120227BitLiuJKPage 12 Types of information:Voice through radio or telephoneVideo picture seen on TV screenDigital Data between mode

8、m and PCImage received by FAXWhat else can you think of?20120227BitLiuJKPage 13 Communication SystemA very simple communication system may include a sender (originator or caller), a receiver and the medium.20120227BitLiuJKPage 14 TelecommunicationsTelecommunications: refers to the transmission of in

9、formation between distant locations by some electromagnetic means. 20120227BitLiuJKPage 15 Data CommunicationsData communications: defined as the interchange and processing encoded information between distant locations using Telecommunications. Encoded information refers to digital information.20120

10、227BitLiuJKPage 16 Computer NetworkNetwork by definition refers to a group of interconnected devices communicating with each other. The device could be telephone exchange. If the device is a computer, it is called computer network.Clustered : Computers are grouped togetherDistributed: This is the cu

11、rrent trend for computer communications.20120227BitLiuJKPage 17 Examples of Clustered Network20120227BitLiuJKPage 18 Example of distributed networks20120227BitLiuJKPage 19 Communication SubnetworkArrangement of the computers and the interconnections between them.DTE: data terminating equipmentDCE: d

12、ata circuit equipment20120227BitLiuJKPage 20 Network ApplicationsThere are numerous applications using networked computers such as:-A central host computer with networked stations.Access to remote program by use of IBM LU 6.2 in local machine.Access to the remote database (Library cataloging system)

13、Financial information (Hong Kong Stock Exchange provided by Reuters)E-commerce, Web-shopping and Electronic Data Interchange (EDI)20120227BitLiuJKPage 21 In class ExerciseLets do Exercise 39 on page 25.“Give two instances of how networks are a part of your life today.”Answer:20120227BitLiuJKPage 22

14、1.1 Data CommunicationComponentsData RepresentationDirection of Data Flow20120227BitLiuJKPage 23 Figure 1.1 Five components of data communicationFive components of data communication: Message, Sender, Receiver, Medium, Protocol20120227BitLiuJKPage 24 In computer information systems, data are represe

15、nted by binary information units (or bits) produced and consumed in the forms of 0s and 1s.Note:Data Representation20120227BitLiuJKPage 25 Characteristics of Data Communication SystemDeliveryData must be received by the correct destination (device or user)AccuracyData must be delivered unchanged. Du

16、e to noise and interference, error detection and correction should be added.TimelinessData must be delivered in time. =Real-time Data should be transmitted to the correct destination in an accurate and timely manner.20120227BitLiuJKPage 26 Data RepresentationText:ASCII - 7 bitsExtended ASCII (8)Unic

17、ode 16 bitsISO - 32 bits!Numbers: BinaryFloating PointImages:VectorBitmap20120227BitLiuJKPage 27 Three Modes of CommunicationSimplex: one direction onlyHalf-Duplex: can be both direction, but only one direction at one timeFull-Duplex: both directions at the same time (simultaneously)What action in d

18、aily life can you think of is similar to these modes?20120227BitLiuJKPage 28 Figure 1.2 Simplex20120227BitLiuJKPage 29 Figure 1.3 Half-duplex20120227BitLiuJKPage 30 Figure 1.4 Full-duplex20120227BitLiuJKPage 31 1.2 NetworksDistributed ProcessingNetwork CriteriaPhysical StructuresCategories of Networ

19、ks20120227BitLiuJKPage 32 Figure 1.5 Point-to-point connection20120227BitLiuJKPage 33 Figure 1.6 Multipoint connection20120227BitLiuJKPage 34 Figure 1.7 Categories of topology20120227BitLiuJKPage 35 Figure 1.8 Fully connected mesh topology (for five devices)20120227BitLiuJKPage 36 Figure 1.9 Star to

20、pology20120227BitLiuJKPage 37 Figure 1.10 Bus topology20120227BitLiuJKPage 38 Figure 1.11 Ring topology20120227BitLiuJKPage 39 Figure 1.12 Categories of networks20120227BitLiuJKPage 40 Figure 1.13 LAN20120227BitLiuJKPage 41 Figure 1.13 LAN (Continued)20120227BitLiuJKPage 42 Figure 1.14 MAN20120227Bi

21、tLiuJKPage 43 Figure 1.15 WAN20120227BitLiuJKPage 44 1.3 The InternetA Brief HistoryThe Internet Today20120227BitLiuJKPage 45 Brief history of InternetSee next slide for the growth of ARPANET(a) Dec 1969(b) July 1970(c) March 1971(d) April 1972(e) Sept 197220120227BitLiuJKPage 46 ARPANETGrowth of th

22、e ARPANET. (a) Dec. 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) Sept. 1972.20120227BitLiuJKPage 47 Figure 1.16 Internet today20120227BitLiuJKPage 48 Internet Computing Capability*Effective computing speed:107 GHz1016 OPS estimated* - too conservative!already exceeded by SETIHOME!Effecti

23、ve storage capacity:104 TB * Clark, David, IEEE Computer, Vol. 34, No. 1 (January 2001), pp18 - 21.20120227BitLiuJKPage 49 World Network Data RatesCityTraffic Tb/sec(1) CityTraffic Tb/sec(1)London18Washington4.0New York13.2San Francisco3.9Amsterdam10.9Toronto3.5Frankfurt10.5Chicago2.7Paris9.7Seattle

24、2.6Brussels6.2Vancouver2.5Geneva5.9Tokyo2.4Stockholm4.4Rate of growth(2)14%(1) E-mail from fengd 28NOV99 at 13:48:50 These numbers seem too large but are interesting if real.(2) / This number is supported by data and seems firm.20120227BitLiuJKPage 50 Growth of Internet Hosts109.5 million in January

25、 2001 (0) 172 million in January 200366.6 million in January 2000 (1)147 million in January 200243.2 million in January 1999(2) /ds/host-count-history.html29.7 million in January 1998(2)16.2 million in January 1997 (2)9.5 million in January 1996 (3)4.9 million in 1995 (3)2.2 million in 1994 (3)1.3 m

26、illion in 1993 (3)(0)Ref:/ds/WWW-200101/index.html(1)Ref:/ Map avail: /mapsale/world/index.html(2)Ref: /ds/WWW-9907/report.html(3)Ref: :8001/people/mkgray/net/internet-growth-summary.html20120227BitLiuJKPage 51 Growth of Internet Hosts* - Graph*Source: Internet Software Consortium /ds/host-count-his

27、tory.html20120227BitLiuJKPage 52 Host AddressingPresentIPv4:32 bits232 (4 x 109) addressesnot realizable because of reserved blocksalready approaching limitFutureIPv6:128 bits2128 (3 x 1038) addresses20120227BitLiuJKPage 53 Number of Unique Web sites by Year1998: 2,636,000*1999: 4,662,000*2000: 7,12

28、8,000* 2001: 8,443,000#2002: 8,712,000#* Source: /oclc/press/20001016a.htm# Source: /stats/size.html20120227BitLiuJKPage 54 June 1999 - Web Sites & PagesWeb sites(1):4.88 million (June 99)Growth rate(1):was 75%/yearWeb pages(2):800 millionClick distance(2):19 clicksReferences:(1)/oclc/research/proje

29、cts/webstats/(2)Science News, September 25, 1999, p203.20120227BitLiuJKPage 55 January 2001 SituationPC clock speed 1.5 GHzInternet hosts (1) : 109.6 millionWeb pages (2): 1,346,966,00(1) /ds/WWW-200101/index.html(2), March 30, 2001 (may contain double listings)20120227BitLiuJKPage 56 January 2003 S

30、ituationPC clock speed 3.2 GHzInternet hosts (1) : 172 millionWeb pages (2): 3,307,998,701 /ds/host-count-history.html, December 25, 2003 (may contain double listings)20120227BitLiuJKPage 57 Extrapolation to Year 2010PC Computing speed: 20 GFLOPSTraffic growth:370% (14% per year)Internet hosts:5.3 b

31、illion (30 x present)Web sites:1.3 billionWeb pages:58.1 billion (18x)Click distance:2220120227BitLiuJKPage 58 1.4 Protocols and StandardsProtocolsStandardsStandards OrganizationsInternet Standards20120227BitLiuJKPage 59 Key Elements of a ProtocolSyntaxData formatsSignal levelsSemanticsControl infor

32、mationError handlingTimingSpeed matchingSequencing20120227BitLiuJKPage 60 StandardsSome are de facto, some are de jureRequired to allow for interoperability between equipmentAdvantagesEnsures a large market for equipment and softwareAllows products from different vendors to communicateDisadvantagesF

33、reeze technologyMay be multiple standards for the same thing20120227BitLiuJKPage 61 Communication OrganizationsITU , International Telecommunication Union, a treaty organization formed in 1865.EIA, This refers to Electronics Industries Association ISO, International Standards Organization (ISO), IEE

34、E , The Institute of Electrical and Electronic Engineers. 20120227BitLiuJKPage 62 Standards OrganizationsInternet SocietyInternet Architecture Board (IAB)Broad guidance and directionInternet Engineering Task Force (IETF)Protocol engineering and developmentInternet Engineering Steering Group (IESG)Management of IETF and standards processISOUS member body is ANSI (American National Stds. Institute)ITU-T (formally CCITT)UN specialized agencyOthers (e.g. ATM forum)20120227BitLiuJKPage 63 IEEE StandardsWide range of electrical and electronic standards of importance /Many of interest to us fro