Introduction to Networks and the Internet CMPE 150 Fall 2005 Lecture 2 CMPE 150 Introduction to Computer Networks 1 Announcements Permission codes Labs Homework 1 CMPE 150 Introduction to Computer Networks 2 Last class What s a computer network Why networks Examples of networks Postal system Telephone network Telephone network Voice Real time CMPE 150 Introduction to Computer Networks 3 Last class cont d The evolution of the telephone system Addressing CMPE 150 Introduction to Computer Networks 4 Today Data networks CMPE 150 Introduction to Computer Networks 5 Data Communication Model Network Source CMPE 150 Introduction to Computer Networks Destination 6 Simplified Communication Model CMPE 150 Introduction to Computer Networks 7 Simplified Data Communications Model CMPE 150 Introduction to Computer Networks 8 CMPE 150 Introduction to Computer Networks 9 Components End systems or hosts Routers switches bridges and Links twisted pair coaxial cable fiber radio etc CMPE 150 Introduction to Computer Networks 10 Components cont d Source generates data to be transmitted Transmitter Converts data into transmittable signals Transmission System Carries data Receiver Converts received signal into data Destination Takes incoming data CMPE 150 Introduction to Computer Networks 11 Key Tasks Transmission Signal Generation Synchronization Error detection and correction Addressing and routing End to end Recovery Security CMPE 150 Introduction to Computer Networks 12 Key Tasks Transmission Signal Generation Synchronization Physical Layer Error detection and correction Addressing and routing End to end Recovery Security Data Link Layer Network Layer Transport Layer Application Layer CMPE 150 Introduction to Computer Networks 13 Networking Point to point communication not usually practical Devices are too far apart Large set of devices would need impractical number of connections Solution is a communications network CMPE 150 Introduction to Computer Networks 14 Simplified Network Model CMPE 150 Introduction to Computer Networks 15 Connecting End Systems Dedicated link Multiple access shared medium CMPE 150 Introduction to Computer Networks 16 Connecting End Systems cont d CMPE 150 Introduction to Computer Networks 17 Shared Communication Infrastructure A stream of packets from sender to receiver CMPE 150 Introduction to Computer Networks 18 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 CMPE 150 Introduction to Computer Networks 19 The Internet Backbone Regional Stub CMPE 150 Introduction to Computer Networks 20 Types of Networks cont d Classification according to type of connection Dedicated link Shared medium multiple access Switched point to point CMPE 150 Introduction to Computer Networks 21 Types of Networks cont d Classification according to topology What is network topology The way network elements are interconnected CMPE 150 Introduction to Computer Networks 22 Network Topologies Examples Star Ring Tree Irregular Bus CMPE 150 Introduction to Computer Networks 23 More Concepts Network protocols Layering Network protocol architecture CMPE 150 Introduction to Computer Networks 24 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 CMPE 150 Introduction to Computer Networks 25 Human and Computer Protocols Human Protocol Computer Protocol Web client open connection OK Hi Hi Got the time Web server send me data 2 00 data time CMPE 150 Introduction to Computer Networks 26 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 CMPE 150 Introduction to Computer Networks 27 Analogy Air Travel The problem air travel Decomposed into series of steps Arrival at airport Departure from airport Check in Baggage claim Boarding Deplane Takeof Landing Traveling CMPE 150 Introduction to Computer Networks 28 Arrival Departure Check in Baggage claim Boarding Deplane Takeof Landing intermediate air traffic sites Airplane routing Arriving airport Departing airport More on the air travel analogy Airplane routing Traveling CMPE 150 Introduction to Computer Networks 29 Protocol Architecture Task of communication broken up into modules For example file transfer could use three modules File transfer application Communication service module Network access module CMPE 150 Introduction to Computer Networks 30 Simplified File Transfer Architecture CMPE 150 Introduction to Computer Networks 31 A Three Layer Model Application Layer Transport Layer Network Access Layer CMPE 150 Introduction to Computer Networks 32 Network Access Layer Exchange of data between the computer and the network Sending computer provides address of destination May invoke levels of service Dependent on type of network used LAN packet switched etc CMPE 150 Introduction to Computer Networks 33 Transport Layer Reliable data exchange Independent of network being used Independent of application CMPE 150 Introduction to Computer Networks 34 Application Layer Support for different user applications e g e mail file transfer CMPE 150 Introduction to Computer Networks 35 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 CMPE 150 Introduction to Computer Networks 36 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
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