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Introduction to Networks and Internet Fundamentals

This lecture explores the foundational concepts of computer networks and the Internet, focusing on their significance and evolution. It covers various types of networks, including Local Area Networks (LANs), Wide Area Networks (WANs), and Metropolitan Area Networks (MANs). The discussion emphasizes network components such as hosts, routers, switches, and communication protocols. It introduces network architecture, highlighting layered protocol design, and the OSI model. Through relatable analogies, this session aims to simplify complex networking concepts and enhance understanding of digital communication.

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Introduction to Networks and Internet Fundamentals

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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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