8/27/2014. What is a computer network? Introduction. Business Applications (1) Uses of Computer Networks. Business Applications (2)

Transcription

1 What is a computer network? Introduction Chapter 1 A number of separate but interconnected computers A collection of autonomous computers interconnected by a single technology COURSE FOCUS: design and organization of computer networks The Internet is not a single network but is a network of networks. The World Wide Web is a distributed system. A distributed system is a software system built on top of a network. 2 Uses of Computer Networks Business Applications (1) Business Applications Home Applications Mobile Users Social Issues A network with two clients and one server Business Applications (2) Home Applications (1) The client-server model involves requests and replies In a peer-to-peer system there are no fixed clients and servers. 1

2 Home Applications (2) Mobile Users Some forms of e-commerce Combinations of wireless networks and mobile computing Social Issues Network Hardware (1) Network neutrality Digital Millennium Copyright Act Profiling users Phishing Transmission technology Broadcast links Point-to-point links 10 Network Hardware (2) Network Hardware (3) Scale Personal area networks Local area networks Metropolitan area networks Wide area networks The internet Classification of interconnected processors by scale. 2

3 Personal Area Network Local Area Networks Bluetooth PAN configuration Wireless and wired LANs. (a) (b) Switched Ethernet. Metropolitan Area Networks Wide Area Networks (1) A metropolitan area network based on cable TV. WAN that connects three branch offices in Australia Wide Area Networks (2) Wide Area Networks (3) WAN using a virtual private network. WAN using an ISP network. 3

4 Wide Area Networks (4) Wide Area Networks (5) Transmission line a) Relation between hosts on LANs and the subnet. 19 A stream of packets from sender to receiver; Store-and-forward or packet-switched subnet Using a routing algorithm, router A decides if a packet should be sent on the line to B or the line to C. 20 Wireless Networks (6) PSTN Network Software Other MSC clusters MSC A base station MSC Other MSC clusters MSC A wireless channel: each mobile device assigned a distinct channel Protocol hierarchies Design issues for the layers Connection-oriented versus connectionless service Service primitives Relationship of services to protocols A mobile/wireless device 21 Protocol Hierarchies (1) Protocol Hierarchies (2) Layers, protocols, and interfaces. The philosopher-translator-secretary architecture 4

5 Protocol Hierarchies (3) Connection-Oriented Versus Connectionless Service Example information flow supporting virtual communication in layer 5. Six different types of service. Service Primitives (1) Service Primitives (2) Six service primitives that provide a simple connection-oriented service A simple client-server interaction using acknowledged datagrams. The Relationship of Services to Protocols Reference Models OSI reference model TCP/IP reference model Model used for this text Comparison of OSI and TCP/IP Critique of OSI model and protocols Critique of TCP/IP model The relationship between a service and a protocol. 5

6 The OSI Reference Model The OSI Reference Model Principles for the seven layers Layers created for different abstractions Each layer performs well-defined function Function of layer chosen with definition of international standard protocols in mind Minimize information flow across interfaces between boundaries Number of layers optimum The OSI reference model OSI Reference Model Layers Physical layer Data link layer Network layer Transport layer Session layer Presentation layer Application layer The TCP/IP Reference Model Layers Link layer Internet layer Transport layer Application layer The TCP/IP Reference Model (1) The TCP/IP Reference Model (2) The TCP/IP reference model The TCP/IP reference model with some protocols we will study 6

7 The Model Used in this Book Comparison of the OSI and TCP/IP Reference Models Concepts central to OSI model Services Interfaces Protocols The reference model used in this book. Critique of the OSI Model and Protocols OSI Model Bad Timing Bad timing. Bad technology. Bad implementations. Bad politics. The apocalypse of the two elephants. Example Networks The ARPANET (1) Internet ARPANET NSFNET Third-generation mobile phone networks Wireless LANs: RFID and sensor networks a) Structure of the telephone system. b) Baran s proposed distributed switching system. 7

8 The ARPANET (2) The ARPANET (3) The original ARPANET design Growth of the ARPANET. a) December b) July c) March The ARPANET (4) NSFNET Growth of the ARPANET. d) April e) September The NSFNET backbone in Architecture of the Internet Third-Generation Mobile Phone Networks (1) Overview of the Internet architecture Cellular design of mobile phone networks 8

9 Third-Generation Mobile Phone Networks (2) Third-Generation Mobile Phone Networks (3) Architecture of the UMTS 3G mobile phone network. Mobile phone handover (a) before, (b) after. Wireless LANs: (1) Wireless LANs: (2) (a) Wireless network with an access point. (b) Ad hoc network. Multipath fading Wireless LANs: (3) RFID and Sensor Networks (1) The range of a single radio may not cover the entire system. RFID used to network everyday objects. 9

10 RFID and Sensor Networks (2) Network Standardization Who s Who in telecommunications Who s Who in international standards Who s Who in internet standards Multihop topology of a sensor network Who s Who in International Standards (1) Who s Who in International Standards (2) The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with gave up and disbanded itself. The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with gave up and disbanded itself. Metric Units (1) Metric Units (2) The principal metric prefixes The principal metric prefixes 10

11 End Chapter 1 11