计算机网络原理(英文版)课件Chapter1-1.ppt

1、计算机网络原理 Computer Network,任课教师：王世普 教授 办 公 室：力行楼2302 联系电话：5032470,电子邮件：spwang,课程要求,了解计算机网络的体系结构，掌握OSI/RM、TCP/IP体系结构 掌握计算机网络协议的概念、协议层次及各层次的主要协议 掌握主要的网络传输介质、数据交换的主要类型及基本原理 掌握应用层协议原理及典型的应用层协议编程 掌握传送层主要原理，熟练掌握TCP、UDP原理及编程 掌握网络层主要原理，熟练掌握协议地址、路由原理 掌握链路层及局域网主要概念、标准、差错控制等原理 了解多媒体网络原理 了解网络安全的相关问题、

2、主要原理 了解网络管理的基本问题,教学安排,教学方法：课堂讲授，课后练习，编程及实习 教学手段：教学课件+多媒体投影 学时安排：讲授54学时，期中考试2学时，实验32学时 （7个必做实验、1个选做实验）。 理论课：期中、期末考核均为闭卷考试 实验课：单列学分，由实验教师按大纲评定成绩。,教材和参考书：,教 材：Computer NetworkingA top-down approach featuring the Internet James F.Kurose/Keith W.Ross 计算机网络 自顶向下的方法与Internet特色 参考书： 1、数据通信与网络技术，清华大学出版社，Data

3、 communication and networking,Behrouz A.Forouzan 2、现代通信网络技术,西南交通大学出版社,曾华燊著. 3、Computer Networks, Fourth Edition By Andrew S. Tanenbaum,（1）Computer Network,What is network? Human network as an example.,Computer Networkthe collection of computers: Connected Via communication links With the target to s

4、hare resources Resources include: computer hardware, software, information (data) and something useful to others,What is computer network?,1.Computer Network definition and structure,In a computer network, Computer is the element of the set.,（2）internet and Internet,Internet is one special internet;

5、 Internet is a world-wide computer network;,What is internet?,What is Internet?,the internet is the interconnection of “Computer Network” Can be seen as the collection of computer networks, i.e. Network of networks.,What support the internet and Internet to run well: Various communication protocols,

6、1、Computer Network definition and structure,internet是指多个网络相互连接构成的网络，并更多地代表网络互连技术； Internet是一个特定的、实际运行的internet，是国际互连网的简称。,Whats the Internet: “nuts and bolts(具体细节)” view,millions of connected computing devices: hosts, end-systems pcs, workstations, servers PDAs, phones, toasters (烘炉) running network

7、 applications routers: forward packets (chunks) of data thru network Other net devices, e.g. switches communication links fiber, copper, radio, satellite,注1 ISP：Internet service Provider,2B,3.2,Whats the Internet: “nuts and bolts” view,protocols: control sending, receiving of messages e.g., TCP, IP,

8、 HTTP, FTP, PPP Internet: “network of networks” loosely hierarchical public Internet versus private Intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force (Internet工程任务组),1B,3.2,（3）The network edge:,end systems (hosts): run application programs e.g., WWW, email a

9、t “edge of network” client/server model client host requests, receives service from server e.g., WWW client (browser)/ server; email client/server peer-peer model minimal (or no) use of dedicated servers e.g.: BT,eMule, Skype,1、Computer Network definition and structure,(3) Network edge: connection-o

10、riented service,Goal: data transfer between end systems. handshaking: setup (prepare for) data transfer ahead of time Hello, hello back human protocol set up “state” in two communicating hosts TCP Connection: like reg. letter In a very loose mode; Only the end systems is aware(明白的); Virtual Connecti

11、on: vs. physical connection in circuit switching.,TCP service RFC 793 TCP - Transmission Control Protocol Internets connection-oriented service reliable, in-order byte-stream data transfer loss: acknowledgements and retransmissions flow control: sender wont overwhelm receiver congestion control: sen

12、ders “slow down sending rate” when network congested,(3) Network edge: connectionless service,Goal: data transfer between end systems same as before! UDP - User Datagram Protocol RFC 768: Internets connectionless service no handshaking no flow control no congestion control unreliable data transfer,A

13、pps using TCP: HTTP (WWW), FTP (file transfer), Telnet (remote login), SMTP (email) Apps using UDP: streaming media, teleconferencing, Internet telephony,（4）The Network Core,mesh of interconnected routers the fundamental question: how is data transferred through net?,circuit switching: a dedicated c

14、ircuit per call as telephone net packet-switching: data sent thru net in discrete “chunks”,1、Computer Network definition and structure,（5）Another view of computer Network,Computer Network = Communication subnet + Resources subnet or Communication subnet + User subnet or Network core + Network edge,1

15、.Computer Network definition and structure,Bus(总线),连接网卡,2. Topological structure of Computer Networks,Terminator (50电阻),Terminator (50电阻),Ex: 10Base-2 Ethernet , 10Mbps,2. Topological structure of Computer Networks,Ring,2. Topological structure of Computer Networks,Ex: Token Ring, 4-16Mbps,2. Topolo

16、gical structure of Computer Networks,IBM8228,Star,2. Topological structure of Computer Networks,Ex: 10BaseT Ethernet, 10Mbps, 100BaseT Ethernet , 100Mbps,2. Topological structure of Computer Networks,3.Network Protocol,A human protocol and a computer network protocol:,Protocols are very important. L

17、earning computer network is focused on learning network protocols, to understanding the what, why, and how of networking protocols.,A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or re

18、ceipt of message or other event. A protocol is a set of rules that govern data communication. It is an agreement between the communication entities. 协议是支配数据通信的规则的集合，是通信实体之间的一种约定。 A protocol defines what is communicated , how it is communicated , and when it is communicated. 协议定义通信的种类、如何通信、什么时候通信。 Th

19、e elements of a protocol are syntax , semantics, and timing. 协议主要包括三个部分： 语法、语义、时序,3. Network Protocol,Syntax: Syntax refers to the structure or format of the data, meaning the order in which they are presented. 语法是指数据的格式或结构，也就是数据字段的排列顺序。 Semantics: Semantics refers to the meaning of each section of

20、bits . 语义是指数据包中每个数据字段的含义。 Timing: Timing refers to two characteristics: when data should be send and how fast they can sent . 时序是指数据在什么时候发送、以多快的速度发送。,3. Network Protocol,Organization of air travel,a series of steps,ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing,ticket

21、 (complain) baggage (claim) gates (unload) runway landing airplane routing,airplane routing,3. Network Protocol,1B，3.3,Layering of airline functionality,Layers: each layer implements a service via own internal-layer actions relying on services provided by layer below,3. Network Protocol,Why layering

22、?,Dealing with complex systems: explicit structure allows identification，relationship of complex systems pieces layered reference model for discussion modularization eases maintenance, updating of system change of implementation of layers service transparent to rest of system e.g., change in gate pr

23、ocedure doesnt affect rest of airline system layering considered harmful?,3. Network Protocol,4. ISO/OSI-7 Layers Model ISO: International Standards Organization OSI: Open System Interconnection Reference Model,4. ISO/OSI-7 Layers Model,Host A,Host B,PDU：Protocol Data Unit,Communication Subnet/Route

24、r,4. ISO/OSI-Data Transmission,Application Layer Services for Processes(进程）: The type of message（报文） exchanged The syntax of the various message types The semantics of fields Rules for determining when and how sends messages and responds to message,4. ISO/OSI-Functions of Layers,Presentation Layer P

25、resentation of Information Message Compression（报文压缩） Conversion between character codes Conversion of file formats Alleviate for other incompatible problems,4. ISO/OSI-Functions of Layers,Session Layer Users Interface into the network Setting up a session connection with a process in another machine

26、. For Example , log in. management of the sessions Conversion session address to transport address close of the session,4. ISO/OSI-Functions of Layers,Transport Layer Host-Host message delivery Source-destination ( end-to-end ) delivery Messages Service-point addressing Segmentation and reassembly C

27、onnect management Flow control Congest control Error control,4. ISO/OSI-Functions of Layers,Network Layer Host-Host Packet Delivery Source-destination ( end-to-end ) delivery Packet Logical addressing routing Error control,4. ISO/OSI-Functions of Layers,Data Link Layer Node-to-Node Frame Delivery No

28、de-to-Node delivery Frame Framing (成帧，帧的封装) Physical addressing Flow control Error control Access control,4. ISO/OSI-Functions of Layers,Physical Layer Transmit a bit stream Transmit a bit stream over a physical medium Representation of bits（Ex. Encoding/Decoding） Data rate ( bits per second , bps)

29、Synchronization of bits ( Sender and receiver ) Line configuration (point-to-point , multipoint) Physical topology (bus, star, ring, etc.） Transmission mode (simplex, half-duplex, duplex),4. ISO/OSI-Functions of Layers,5. TCP/IP Model,TCP,UDP,IP,RARP,ARP,TCP/IP Layer,ISO/OSI Layer,application: suppo

30、rting network applications FTP, SMTP, HTTP transport: host-host data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements PPP, Ethernet physical: bits “on the wire”,5. TCP/IP Model-Internet protocol stack,source,router,5