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Introduction to Computer Networks

This chapter provides an overview of computer networks, including the client-server model, home network applications, peer-to-peer systems, network scale terminology, network links, local area networks, metropolitan area networks, wide area networks, wireless networks, network software, protocol hierarchies, and reference models.

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Introduction to Computer Networks

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  1. Introduction Chapter 1 Adapted from Tanenbaum's Slides for Computer Networks, 4e

  2. Use Scenarios for Networks • Access to remote information • Person-to-person communication • Interactive entertainment • Electronic commerce

  3. Client-Server • A network with two clients and one server.

  4. Client-Server (2) • The client-server model involves requests and replies.

  5. Home Network Applications • Access to remote information • Person-to-person communication • Interactive entertainment • Electronic commerce

  6. Peer-to-Peer • In peer-to-peer system there are no fixed clients and servers. • Our main concern in this class: how do messages get from application on one machine to client or server or peer on another. • Beyond that lies distributed systems, CptS 464/564

  7. Network Scale Terminology • Classification of interconnected processors by scale.

  8. Network Links • Two types of data transmission technology • Broadcast links • Point-to-point links

  9. Local Area Networks • Three broadcast networks • (a) Bus • (b) Ring • (c) Star

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

  11. Wide Area Networks • Relation between hosts on LANs and the subnet. • (Note: this use of subnet is uncommon these days. Network Backbone is more typical for a closely related concept.)

  12. Wide Area Networks (2) • A stream of packets from sender to receiver. • (Note: not all packets need to take the same path!)

  13. Wireless Networks • (a) Bluetooth or infrared personal network • (b) Wireless LAN (Wireless ethernet/WiFi) • (c) Wireless MAN (WiMax)

  14. Amazing thing: all these technologies work together to interconnect computers around the world. How?

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

  16. Network SoftwareProtocol Hierarchies – the abstract story • Layers, protocols, and interfaces.

  17. Protocol Hierarchies (Example) • The philosopher-translator-secretary architecture.

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

  19. Design Issues in each Layer • Addressing • Error Control • Flow Control • Multiplexing • Routing • And, relative to its neighbor layes, its Interface (or service description)

  20. Example Services • Six different types of service.

  21. Service Primitives • Five service primitives for implementing a simple connection-oriented service. Where are they implemented in the hierarchy?

  22. Services to Protocols Relationship • The relationship between a service and a protocol.

  23. 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

  24. Reference Models The OSI reference model.

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

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

  27. Comparing OSI and TCP/IP Models • Concepts central to the OSI model • Services • Interfaces • Protocols

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

  29. Bad Timing • The apocalypse of the two elephants.

  30. 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

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

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

  33. The ARPANET (2) • The original ARPANET design.

  34. The ARPANET (3) • Growth of the ARPANET (a) December 1969. (b) July 1970. • (c) March 1971. (d) April 1972. (e) September 1972.

  35. NSFNET • The NSFNET backbone in 1988.

  36. Architecture of the Internet • Overview of the Internet.

  37. Ethernet • Architecture of the original Ethernet.

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

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

  40. Wireless LANs (3) • A multicell 802.11 network.

  41. Metric Units • The principal metric prefixes.

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