1. CMPE 80N - Introduction to Networks and the Internet 1 CMPE 80N Winter 2004 Lecture 2 Introduction to Networks and the Internet

2. CMPE 80N - 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. CMPE 80N - Introduction to Networks and the Internet 3 Last class (cont’d) The evolution of the telephone system. Addressing. Data networks.

4. CMPE 80N - Introduction to Networks and the Internet 4 Data Networks Components: –End systems (or hosts), –Routers/switches/bridges, and –Links (twisted pair, coaxial cable, fiber, radio, etc.).

5. CMPE 80N - Introduction to Networks and the Internet 5 Communication Model Network SourceDestination

6. CMPE 80N - Introduction to Networks and the Internet 6 Connecting End Systems Dedicated link Multiple access / shared medium

7. CMPE 80N - Introduction to Networks and the Internet 7 Connecting End Systems (cont’d) Router Switched network Router: switching element; a.k.a., IMPs (Interface Message Processors) in ARPAnet’s terminology.

8. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 9 The Internet Backbone Regional Stub

10. CMPE 80N - Introduction to Networks and the Internet 10 Types of Networks (cont’d) Classification according to type of connection. –Dedicated link. –Shared medium (multiple access). –Switched point-to-point.

11. CMPE 80N - Introduction to Networks and the Internet 11 Types of Networks (cont’d) Classification according to topology… What is network topology? –The way network elements are interconnected.

12. CMPE 80N - Introduction to Networks and the Internet 12 Network Topologies: Examples Star Ring Tree Irregular

13. CMPE 80N - Introduction to Networks and the Internet 13 More Concepts… Network protocols. Layering. Network architecture.

14. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 15 Human and Computer Protocols Hi Got the time? 2:00 time Human ProtocolComputer Protocol Web client Web server open connection OK send me data

16. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 17 Analogy: Air Travel The problem: air travel. Decomposed into series of steps: Arrival at airport Check-in Boarding Takeoff Departure from airport Baggage claim Deplane Landing Traveling

18. CMPE 80N - Introduction to Networks and the Internet 18 More on the air travel analogy… Arrival Check-in Boarding Takeoff Departing airport Departure Baggage claim Deplane Landing Arriving airport Traveling intermediate air traffic sites Airplane routing

19. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 22 Network Architecture Set of layers, what their functions are, the services each of them provide, and the interfaces between them.

23. CMPE 80N - Introduction to Networks and the Internet 23 Example 1: ISO OSI Architecture ISO: International Standards Organization OSI: Open Systems Interconnection. Physical Data link Network Transport Session Presentation Application

24. CMPE 80N - Introduction to Networks and the Internet 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. CMPE 80N - Introduction to Networks and the Internet 25 Example 2: TCP/IP Architecture Model employed by the Internet. Physical Data link Network Transport Session Presentation Application Transport Internet Network Access Physical TCP/IP ISO OSI