信息網(wǎng)絡(luò)通信基礎(chǔ)

1、Data Communications & NetworkingChapter 1Introduction第一章第一章 緒論緒論Department of Electronic and Communication EngineeringNCEPU1Data Communications & Networking2Data Communications & Networking3Data Communications & Networking4Data Communications & NetworkingChapter 1Introduction緒論緒論

2、5Data Communications & NetworkingComponents 組成組成Data Representation 數(shù)據(jù)表示數(shù)據(jù)表示Data Flow 數(shù)據(jù)流數(shù)據(jù)流6Data Communications & Networking Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. The effectiveness of a data communications

3、 system depends on four fundamental characteristics:1. Delivery. 傳遞性 The system must deliver data to the correct destination2. Accuracy. 準(zhǔn)確性3. Timeliness. 及時(shí)性4. Jitter. 抖動(dòng)性 Jitter refers to the variation in the packet arrival time. (audio or video)7Data Communications & NetworkingFigure 1.1 Five

4、 components of data communication1. Message 報(bào)文報(bào)文 2. Sender 發(fā)送方發(fā)送方 3. Receiver 接受方接受方 4. Medium 介質(zhì)介質(zhì)5. Protocol 協(xié)議協(xié)議8Data Communications & Networking Text 文本 Numbers 數(shù)字 Images 圖像 Audio 音頻 Video 視頻9Data Communications & NetworkingFigure 1.2 Data flow (simplex, half-duplex, and full-duplex)p6 數(shù)

5、據(jù)流分為單工、半雙工和雙工數(shù)據(jù)流分為單工、半雙工和雙工10Data Communications & Networking網(wǎng)絡(luò)是指由介質(zhì)鏈路連接在一起的一系列設(shè)備（常常被稱為網(wǎng)絡(luò)節(jié)點(diǎn)）Distributed Processing Network Criteria Physical StructuresNetwork Models網(wǎng)絡(luò)模型網(wǎng)絡(luò)模型Categories of NetworksInterconnection of Networks: Internetwork11Data Communications & NetworkingAdvantages:1. Security

6、/encapsulation 安全性安全性/封裝性封裝性2. Distributed databases 分布式數(shù)據(jù)庫分布式數(shù)據(jù)庫3. Faster problem solving 更快的解決問題方式更快的解決問題方式4. Security through redundancy 通過冗余達(dá)到通過冗余達(dá)到安全性安全性5. Collaborative processing 協(xié)作處理協(xié)作處理12Data Communications & Networking性能：多種形式衡量，包括傳輸時(shí)間和響應(yīng)時(shí)間。性能取決于多種因素用戶數(shù)量、傳輸介質(zhì)類型、所連接的硬件能力以及軟件效率可靠性：出現(xiàn)故障的頻率

7、、一條鏈路從故障恢復(fù)所花費(fèi)的時(shí)間可靠性：保護(hù)數(shù)據(jù)免受未授權(quán)的訪問13Data Communications & NetworkingFigure 1.3 Types of connections: point-to-point and multipoint點(diǎn)到點(diǎn)點(diǎn)到點(diǎn)和多點(diǎn)和多點(diǎn)Reserved capacity VS Shared capacity連接類型物理結(jié)構(gòu)物理結(jié)構(gòu) Physical Structures14Data Communications & NetworkingFigure 1.4 Categories of topology物理拓?fù)浣Y(jié)構(gòu)15Data Comm

8、unications & NetworkingFigure 1.5 A fully connected mesh topology (five devices)優(yōu)點(diǎn):1.專用線路dedicated links2.健壯性 robust3.秘密性、安全性privacy/security4.故障識(shí)別、排除fault identification/ isolation5. 缺點(diǎn)：6.安裝復(fù)雜，費(fèi)用離譜16Data Communications & NetworkingnExample The Lucky Ducky Corporation has a fully connected m

9、esh network consisting of eight devices. Calculate the total number or cable links needed and the number of ports for each devices.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

10、 stationsA dedicated point-to-point link only to a central controller, hub星型拓?fù)溆糜诰钟蚓W(wǎng)中，高速局域網(wǎng)通常用星型拓?fù)浣Y(jié)構(gòu)18Data Communications & NetworkingFigure 1.7 A bus topology connecting three stationsUsed in early Ethernet LANs but they are less pupular now.總線拓?fù)涫嵌帱c(diǎn)配置的(multipoint)。Ease of installation; less cabl

11、ing; 易安裝，使用電纜最少，主纜能支持的抽頭數(shù)和抽頭之間的距離都有限制，在各個(gè)抽頭處的信號(hào)反射會(huì)降低傳輸質(zhì)量。健壯性差(robustness)引出線引出線分接頭分接頭19Data Communications & NetworkingFigure 1.8 A ring topology connecting six stations被IBM引入令牌環(huán)局域網(wǎng)時(shí)曾盛行一時(shí)，目前要求高速局域網(wǎng)，這種拓?fù)浣Y(jié)構(gòu)就不流行了。Example 1.2If the devices in Example 1.1 are configured as a ring instead of a mesh, h

12、ow 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 & Networking Network Models 網(wǎng)絡(luò)模型OSI 7-layer modelInternet 5-layer model Categories of Networks 網(wǎng)絡(luò)分類Local Area Network 局域網(wǎng)Wide Area

13、 Network 廣域網(wǎng)Metropolitan Area Network 城域網(wǎng)Interconnection of Networks: Internetwork網(wǎng)絡(luò)互聯(lián)：因特網(wǎng)22Data Communications & NetworkingFigure 1.10 An isolated LAN connecting 12 computers to a hub in a closet房間房間Currently, LAN size is limited to a few kilometers. Common LAN topologies: bus, ring, and star.S

14、peeds 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 Communications & Networking1.12 A heterogeneous network made of four WANs and two LANsInternetworkheterogeneous不同種類的不同種類的25Data Co

15、mmunications & Networking因特網(wǎng)因特網(wǎng)A Brief History 歷史簡(jiǎn)介歷史簡(jiǎn)介The Internet Today (ISPs) 因特網(wǎng)現(xiàn)狀（因特網(wǎng)服務(wù)提供商）因特網(wǎng)現(xiàn)狀（因特網(wǎng)服務(wù)提供商）26Data Communications & Networking , ARPA署長-赫茲菲爾德 27Data Communications & Networking 28Data Communications & NetworkingChronology of Internet Evolution29Data Communications

16、& NetworkingFigure 1.13 Hierarchical organization of the InternetISP：Internet Service Provider30Data Communications & NetworkingProtocols協(xié)議協(xié)議Standards標(biāo)準(zhǔn)標(biāo)準(zhǔn)Standards Organizations 標(biāo)準(zhǔn)化組織標(biāo)準(zhǔn)化組織Internet Standards 因特網(wǎng)標(biāo)準(zhǔn)因特網(wǎng)標(biāo)準(zhǔn)31Data Communications & NetworkingPerformance Number of usersType of tr

17、ansmission mediumHardware Software Reliability Frequency of failure 故障頻率故障頻率Recovery time of a network after a failure 網(wǎng)絡(luò)故障恢復(fù)時(shí)間網(wǎng)絡(luò)故障恢復(fù)時(shí)間Catastrophe 災(zāi)難性事故災(zāi)難性事故Security Unauthorized access 未授權(quán)訪問未授權(quán)訪問Viruses 病毒病毒32In data communication, a protocol is a set of rules (conventions) that govern all aspects

18、of information communication在數(shù)據(jù)通信中在數(shù)據(jù)通信中, 協(xié)議是指一組用來控制信息通信協(xié)議是指一組用來控制信息通信的各個(gè)方面的規(guī)則的各個(gè)方面的規(guī)則(約定約定)33Data Communications & NetworkingStandards OrganizationsStandards Creation Committees 標(biāo)準(zhǔn)化組織Forums 論壇：quickly test, evaluate, and standardize new technologies. Regulatory Agencies 管理機(jī)構(gòu)34Data Communications & NetworkingStandard