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1、Computer Networks,计算机与控制学院 王鑫,参考文献,Andrew S. Tanenbaum, Computer Networks (Fourth Edition), 清华大学出版社 & Prentice Hall, 2004 James F. Kurose等著，陈鸣译. 计算机网络自顶向下方法与Internet特色（第三版）.机械工业出版社，2005 谢希仁.计算机网络（第四版）.电子工业出版社，2003,Contents,Introduction(7),1,The Physical Layer(5),2,The Data Link Layer(6),3,The MAC Su
2、b-layer(6),4,The Network Layer(6),5,The Transport Layer(4),6,The Application Layer(4),7,Network Security(4),8,1 Introduction,学习目的：了解计算机网络发展历史、计算机网络的分类、网络体系结构（OSI/RM、TCP/IP）、计算机网络相关的基本概念和交换技术等。 学习重点：熟练掌握计算机网络、网络协议、网络体系结构等三个重要概念。 学习难点：掌握三种交换技术之间的异同。,What is computer networks?,Computer Network: means a
3、 collection of autonomous computers（自主/自治计算机） interconnected. It is composed of hosts, protocols and communication-subnet. The difference between Computer Network and Distributed System Distributed System: A collection of autonomous (independent) computers is transparency（透明的）to its users. It is a s
4、oftware system built on top of a network. Thus, the key distinction between a network and a distributed system is the software (especially the operating system: NOS and Distributed OS), rather than the hardware.,The development of computer networks,First, Terminal-oriented network （1）Computing techn
5、ology and communication technology. （2）Circuit-exchange(电路交换): Connection establishment, Data transform, Connection release. Second, Packet-exchange network: 1969.11, ARPANET,The development of computer networks,(a) Circuit switching (b) Message switching (c) Packet switching,The development of comp
6、uter networks,Third, Network Architecture IBM：SNA(系统网络体系结构)，1974，the first architecture of network ISO：OSI/RM(开放系统互连基本参考模型,Reference model) TCP/IP：Internet Digital：DNA(Distributed network architecture, 分布式系统体系结构) Fourth, Wide Band(Broad band) network Broad Band and Integrated,1.1 Uses of Computer Ne
7、tworks,Business Applications Home Applications Mobile Users Social Issues,Business Applications,The goals of the computer networks: Resource sharing （hardware 、software and Data，资源共享）Communication medium（通信手段）,Home Applications,Access to remote information(访问远程信息) Person to person communication(个人间通
8、信) Interactive entertainment(交互式娱乐) Ecommerce(电子商务),1.2 Network Hardware,Local Area Networks Metropolitan Area Networks Wide Area Networks Wireless Networks Home Networks Internetworks,Broadly speaking(从广义上讲)，two types of transmission technology: （1）Broadcast links （2）Point-to-point links Broadcast
9、network(广播式网络)：broadcasting and multicasting Point-to-point network(点到点网络)：packettransmission(分组转发) and routingalgorithms（路由选择）,Local Area Networks(局域网),Three characteristics: (1)Size(范围) (2)Transmission technology(传输技术) (3)Topology(拓扑结构),Metropolitan Area Networks(城域网),A metropolitan area network b
10、ased on cable TV,Wide Area Networks(广域网),Wireless Networks,Categories of wireless networks: System interconnection Wireless LANs Wireless WANs,（a）Bluetooth （b）Wireless LAN,Home Networks,Computers (desktop PC, PDA, shared peripherals Entertainment (TV, DVD, VCR, camera, stereo, MP3) Telecomm (telepho
11、ne, cell phone, intercom, fax) Appliances (microwave, fridge, clock) Telemetry(遥感，遥测) (utility meter（电表）, burglar alarm（防盗自动警铃）, babycam （婴儿监护器）).,The first homework,P180：NO.42, NO.43,1.3 Network Software,Protocol Hierarchies Design Issues for the Layers Connection-Oriented and Connectionless Servic
12、es Service Primitives The Relationship of Services to Protocols,Protocol Hierarchies(协议分层),To reduce their design complexity, most networks are organized as a stack of layers or levels. Advantages of Protocol Hierarchies:(分层的优点) (1) Independence of layers: These layers are relative independence.(各层之
13、间是相对独立的) (2) If any layer is changed, other layers are not affected, so far as not changing interface. (灵活性好) (3) Each layer can be realized in right technology.(结构上可以分割开) (4) It is easy to realize and maintain. (易于实现和维护) (5) Standardization (能促进标准化工作),Protocol Hierarchies(协议分层),Defects of Protocol
14、Hierarchies:(分层的缺点) (1)Some functions may be realized repeatedly. (功能重复实现，资源浪费) (2) The number of layer is not certain.(层次数难以确定),Example,机票 (购买)行李 (托运)旅客 (出发)飞机 (起飞)飞行航线,机票 (投诉)行李 (认领)旅客 (到达)飞机 (着陆)飞行航线,飞行航线,Example,层次的观点： - 每层实现一种特定的服务- 通过自己内部的功能- 依赖自己的下层提供的服务,机票 (购买)行李 (托运)旅客 (出发)飞机 (起飞)飞行航线,机票 (投
15、诉)行李 (认领)旅客 (到达)飞机 (着陆)飞行航线,飞行航线,Example,分层的空中旅行组织: 服务,从出发地到目的地的航线：导航服务,柜台-to-柜台：“旅客+行李” 票务服务,行李托运-to-行李认领：行李服务,登机入口-to-到达出口：旅客乘务服务,跑道-to-跑道：飞机“航运”服务,Protocol Hierarchies(协议分层),Protocol Hierarchies(协议分层),Protocol Hierarchies(协议分层),Protocol is an agreement between the communicating parties on how com
16、munication is to proceed. Three factors：Syntax（语法），Semantics（语义），Synchronous（同步） Network architecture is a set of layers and protocols The difference of Protocol、Service and SAP,Design Issues for the Layers,(1)A mechanism for identifying senders and receivers. (2)The rules for data transfer: Simplex communication(单工通信)Half-duplex communication(半双工通信)Full-duplex communication(全双工通信) (3)Error control(差错控制) (4)Flow control(流量控制) (5)Disassembling(分割) and gathering（合并）messages (6)Multiplexing(多路复用) and demultiplexing(多路分用、解多路复用) (7)Routing(路由选择),
