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CMPE 80N Winter 2004 Lecture 2

CMPE 80N Winter 2004 Lecture 2. Introduction to Networks and the Internet. Last class…. What’s a computer network? Why networks? Examples of networks: Postal system. Telephone network. Telephone network: Voice. Real-time. Last class (cont’d). The evolution of the telephone system.

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CMPE 80N Winter 2004 Lecture 2

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  1. CMPE 80NWinter 2004Lecture 2 Introduction to Networks and the Internet

  2. Last class… • What’s a computer network? • Why networks? • Examples of networks: • Postal system. • Telephone network. • Telephone network: • Voice. • Real-time.

  3. Last class (cont’d) • The evolution of the telephone system. • Addressing. • Data networks.

  4. Data Networks • Components: • End systems (or hosts), • Routers/switches/bridges, and • Links (twisted pair, coaxial cable, fiber, radio, etc.).

  5. Communication Model Network Source Destination

  6. Connecting End Systems Dedicated link Multiple access / shared medium

  7. Connecting End Systems (cont’d) Router Switched network Router: switching element; a.k.a., IMPs (Interface Message Processors) in ARPAnet’s terminology.

  8. Types of Data Networks • Several ways to classify data networks. • For example, according to “coverage”: • Local Area Networks (LANs) typically provide networking capabilities within a building, campus. • Typically within 5-mile radius. • Wide-Area Networks (WANs) span greater geographic distances (e.g., world-wide). • Metropolitan Area Networks (MANs) span more restricted distances, e.g., geographic regions (e.g., Los Nettos network in Southern California, etc.)

  9. The Internet Backbone Regional Stub

  10. Types of Networks (cont’d) • Classification according to type of connection. • Dedicated link. • Shared medium (multiple access). • Switched point-to-point.

  11. Types of Networks (cont’d) • Classification according to topology… • What is network topology? • The way network elements are interconnected.

  12. Network Topologies: Examples Ring Tree Star Irregular

  13. More Concepts… • Network protocols. • Layering. • Network architecture.

  14. Network Protocols • Diplomats use rules, called protocols, as guides for formal interactions. • A communication protocol is a set of rules that specify the format and meaning of messages exchanged between computers across a network. • A set of related protocols that are designed for compatibility are called protocol suite.

  15. Human Protocol Computer Protocol Hi Hi Got the time? 2:00 <data> time Human and Computer Protocols Web client open connection Web server OK send me data

  16. Layering • What is it? • Building complex systems is hard! • Approach: “Divide and conquer”. • Split job into smaller jobs, or layers. • Analogy to other fields. • Building a house: digging, foundation, framing, etc. • Car assembly line… • Basic idea: each step dependent on the previous step but does not need to be aware of how the previous step was done.

  17. Analogy: Air Travel • The problem: air travel. • Decomposed into series of steps: Departure from airport Baggage claim Deplane Landing Arrival at airport Check-in Boarding Takeoff Traveling

  18. Departure Baggage claim Deplane Landing Arrival Check-in Boarding Takeoff Arriving airport Departing airport Traveling Airplane routing Airplane routing intermediate air traffic sites More on the air travel analogy…

  19. Layered Protocol Design • Layering model is a solution to the problem of complexity in network protocols • The model divides the network protocols into layers, each of which solves part of the network communication problem • Each layer has its own protocol! • Each layer implements a service to the layer above • Relying on services provided by the layers below.

  20. Layers • Layers are the different components that need to be designed/implemented when designing/implementing networks. • Each layer responsible for a set of functions. • Top layer relies on services provided by bottom layer. • Layer makes it service available to higher layer through an interface.

  21. Network Architecture • Set of layers, what their functions are, the services each of them provide, and the interfaces between them. • A.k.a, protocol stack. • Examples: • ISO-OSI 7 layer architecture. • TCP-IP architecture (Internet).

  22. Network Architecture • Set of layers, what their functions are, the services each of them provide, and the interfaces between them.

  23. Example 1: ISO OSI Architecture • ISO: International Standards Organization • OSI: Open Systems Interconnection. Application Presentation Session Transport Network Data link Physical

  24. Layers of Interest in ISO Model • Layer 7: Application • Application-specific protocols (e.g. ftp, http, smtp) • Layer 4: Transport • Delivery of data between computers (end-to-end). • Layer 3: Network • Data routing across a network. • Layer 2: Data Link • Reliable transmission over physical medium. • Layer 1: Physical • - Transmission of bits between two nodes.

  25. Example 2: TCP/IP Architecture • Model employed by the Internet. ISO OSI TCP/IP Application Application Presentation Session Transport Transport Internet Network Network Access Data link Physical Physical

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