Module 1 Introduction Data Communication n Networks n

Module 1: Introduction Data Communication n Networks n Protocols and Standards n Standard Organizations n 1 Module 1 Computer Networks 1

Definitions n n 2 Computer Network: an interconnected collection of autonomous computers, printers, peripherals, etc. Distributed system: a software system built on top of a network. Module 1 Computer Networks 2

Distributed Systems Vs. Computer Networks n In Distributed Systems n n n In Computer Networks n 3 Computers are transparent to the user. Everything is handled automatically by the system. Users must explicitly supply addresses, explicitly submit jobs, move files around, …etc. . Module 1 Computer Networks 3

Why Computer Networks §Resource Sharing §High Reliability §Access to Remote Information §Communication §Interactive Entertainment §Saving Money: Client-Server Model 4 Module 1 Computer Networks 4

Data Communication System Components 5 Module 1 Computer Networks 5

Data Representation n Text – represented as a bit pattern; codes often used: n n n 6 ASCII; Extended ASCII; Unicode; ISO Numbers – represented by binary equivalent Images – bit patterns representing pixels Audio Video Module 1 Computer Networks 6

Data Communication Network Criteria Performance 7 Module 1 Reliability Computer Networks Security 7

Performance §Number of Users §Type of Transmission Medium §Hardware §Software 8 Module 1 Computer Networks 8

Reliability §Frequency of Failure §Recovery Time §Catastrophe 9 Module 1 Computer Networks 9

Security §Unauthorized access §Viruses 10 Module 1 Computer Networks 10

Applications §Home Application §Business Application §Mobile Applications 11 Module 1 Computer Networks 11

Protocols § Protocol: a set of rules that govern data communication. § It defines § What is communicated § How it is communicated § When it is communicated 12 Module 1 Computer Networks 12

Protocol Elements n n n 13 Syntax: the structure or format of the data, meaning the order in which they are presented. Semantics: the meaning of section of bits. Timing: refers to when data should be sent and how fast it can be sent. Module 1 Computer Networks 13

Why Standards §To guarantee interoperability and compatibility of networks. 14 Module 1 Computer Networks 14

Categories of standards Standards De facto (by fact) 15 Module 1 De jure ( by law) Computer Networks 15

De facto Standards §Proprietary standards (Closed) invented by a company as a basis for the operation of its product. §Nonproprietary standards (Open) developed by groups or committees that have passed them into the public. 16 Module 1 Computer Networks 16

De Jure Standards §Legislated by an officially recognized body. 17 Module 1 Computer Networks 17

Standards Organizations §International Standards Organization (ISO): dedicated to worldwide agreement on international standards in a variety of fields. §International Telecommunication Union- Telecommunication Sector (ITU-T): Develop standards for telecommunications. 18 Module 1 Computer Networks 18

Standards Organizations §American National Standards Institute (ANSI): U. S. voting representative to both ISO and ITUT. §Institute of Electrical and Electronics Engineers (IEEE): the largest national professional group in developing standards for computing, communication, electrical engineering, and electronics. 19 Module 1 Computer Networks 19

Standards Organizations n n 20 Electronic Industries Association (EIA): an association of electronics manufacturers in the U. S. Telcordia Module 1 Computer Networks 20