Chapter 1. Introduction

Transcription

1 Chapter 1 Introduction

2 Computer Networks The old model of a single computer serving all of the organization s computational needs has been replace by one in which a large number of separate but interconnected computers do the job. These system are called Computer Networks. The term Computer Networks to mean a collection of autonomous computer interconnected by a single technology. The distributed system is a collection of independent computers to its user as a single coherent system.

3 Uses of Computer Networks Business Applications Home Applications Mobile Users Social Issues

4 Business Applications of Networks - Resource Sharing. - Clients servers - Clients servers model - Provide powerful communication medium among employees. - ; E-commerce;

5 Business Applications of Networks (2) The client-server model involves requests and replies.

6 Home Network Applications Access to remote information Comes in many forms; Instant messaging; Social networks; Person-to-person communication peer to peer communication; Napster; Bit Torrent; file sharing Mobile users; WAP; Social Issues; Interactive entertainment Electronic commerce

7 Home Network Applications (2) In peer-to-peer system there are no fixed clients and servers.

8 Home Network Applications (3) Some forms of e-commerce.

9 Mobile Network Users Combinations of wireless networks and mobile computing.

10 Network Hardware Local Area Networks Metropolitan Area Networks Wide Area Networks Wireless Networks Home Networks Internetworks

11 Broadcast Networks Types of transmission technology Broadcast links Point-to-point links

12 Broadcast Networks (2) Classification of interconnected processors by scale.

13 Local Area Networks Two broadcast networks a) Bus : IEEE Ethernet; bus-based broadcast network with decentralized control. b) Ring: IEEE Token Ring; FDDI.

14 Metropolitan Area Networks A metropolitan area network based on cable TV.

15 Wide Area Networks Relation between hosts on LANs and the subnet. Hosts Communication subnet (subnet): organized by store and forward or packet switched. Transmission line Switching elements: router. Routing Algorithms

16 Wide Area Networks (2) A stream of packets from sender to receiver.

17 Wireless Networks Categories of wireless networks: Inspired by Morse Code System interconnection Wireless LANs : IEEE Wireless WANs Bluetooth The King s Name (Built up by consortium including Ericsson, Nokia, Motorola and others)

18 Wireless Networks (2) (a) Bluetooth configuration (b) Wireless LAN

19 Wireless Networks (3) (a) Individual mobile computers (b) A flying LAN

20 Home Network Categories Computers (desktop PC, PDA, shared peripherals Entertainment (TV, DVD, VCR, camera, stereo, MP3) Telecomm (telephone, cell phone, intercom, fax) Appliances (microwave, fridge, clock, furnace, airco) Telemetry (utility meter, burglar alarm, babycam).

21 Network Software Protocol Hierarchies Design Issues for the Layers Connection-Oriented and Connectionless Services Service Primitives The Relationship of Services to Protocols

22 Network Software Protocol Hierarchies Layers, protocols, and interfaces.

23 Protocol Hierarchies (2) Location A Location B 3 I like rabbits Message Philosopher J'aime bien les lapins 3 2 L: Dutch Ik vind konijnen leuk Information for the remote translator Translator L: Dutch Ik vind konijnen leuk 2 1 Fax #--- L: Dutch Ik vind konijnen leuk Information for the remote secretary Secretary Fax #--- L: Dutch Ik vind konijnen leuk 1 The philosopher-translator-secretary architecture.

24 Protocol Hierarchies (3) Example information flow supporting virtual communication in layer 5.

25 Design Issues for the Layers Addressing: specify a specific destination Error Control : important issue because physical communication circuits are not perfect Flow Control : how to keep a fast sender from swamping a slow receiver with data. Multiplexing : reducing the inconvenient or expensive connection for each pair of communicating processes Routing : when multiple paths between source and destination, route must be chosen.

26 Connection-Oriented and Connectionless Services Six different types of service.

27 Service Primitives Five service primitives for implementing a simple connectionoriented service.

28 Service Primitives (2) Packets sent in a simple client-server interaction on a connection-oriented network.

29 Services to Protocols Relationship The relationship between a service and a protocol. Service is a set of primitives that a layer provides to the layer above it. Protocol is a set of rules governing the format and meaning of the packets A protocol relates to the implementation of service and as such is not visible to the user of the service.

30 Reference Models The OSI Reference Model The TCP/IP Reference Model A Comparison of OSI and TCP/IP A Critique of the OSI Model and Protocols A Critique of the TCP/IP Reference Model

31 The OSI reference model. Reference Models

32 Reference Models (2) The TCP/IP reference model.

33 Reference Models (3) Protocols and networks in the TCP/IP model initially.

34 Comparing OSI and TCP/IP Models Concepts central to the OSI model Services Tells what the layer does. Interfaces Tells the processes above it how to access it. Specify the parameters Protocols Used in the layer as the layer s own business

35 A Critique of the OSI Model and Protocols Why OSI did not take over the world Bad timing Bad technology Bad implementations Bad politics

36 Bad Timing The apocalypse of the two elephants. When the subject is first discovered, there is a burst of research activities in the forms of discussion, paper and meetings. After a while this activities subsides, corporations discover the subject and the billion dollar wave of investments hits.

37 A Critique of the TCP/IP Reference Model Problems: Service, interface, and protocol not distinguished Not a general model Host-to-network layer not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace

38 Hybrid Model The hybrid reference model to be used in this book.

39 The Internet Example Networks Connection-Oriented Networks: X.25, Frame Relay, and ATM Ethernet Wireless LANs: 802:11

40 The ARPANET (a) Structure of the telephone system. (b) Baran s proposed distributed switching system.

41 The ARPANET (2) The original ARPANET design.

42 The ARPANET (3) Growth of the ARPANET (a) December (b) July (c) March (d) April (e) September 1972.

43 NSFNET The NSFNET backbone in 1988.

44 Internet in Malaysia - JARING - Joint Action Research Integrated Networking - MIMOS. - Dial Up technology First Internet Provider - TMNET - Telekom Malaysia - Dial Up technology

45 Internet Usage Traditional applications ( ) News Remote login File transfer

46 Architecture of the Internet Overview of the Internet.

47 ATM Virtual Circuits A virtual circuit.

48 ATM Virtual Circuits (2) An ATM cell.

49 The ATM Reference Model The ATM reference model.

50 The ATM Reference Model (2) The ATM layers and sublayers and their functions.

51 Ethernet Architecture of the original Ethernet.

52 Wireless LANs (a) Wireless networking with a base station. (b) Ad hoc networking.

53 Wireless LANs (2) The range of a single radio may not cover the entire system.

54 Wireless LANs (3) A multicell network.

55 Network Standardization Who s Who in the Telecommunications World AT&T PTT ITU Who s Who in the International Standards World ISO ANSI; BSI; AFNOR; DIN and 85 others NIST; IEEE Who s Who in the Internet Standards World IAB FRC technical report IRTF IETF

56 ITU Main sectors Radiocommunications Telecommunications Standardization Development Classes of Members National governments Sector members Associate members Regulatory agencies

57 IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with gave up.

58 Metric Units The principal metric prefixes.