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CS3502: Data and Computer Networks INTRODUCTION

CS3502: Data and Computer Networks INTRODUCTION. introduction: CS3502. overview of computer networks Track course objectives homeworks, tests, grading approximate schedule. objectives: CS3502. gain good overview of networking detailed knowledge of physical layer data link layer

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CS3502: Data and Computer Networks INTRODUCTION

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  1. CS3502:Data and Computer NetworksINTRODUCTION

  2. introduction: CS3502 • overview of computer networks Track • course objectives • homeworks, tests, grading • approximate schedule

  3. objectives: CS3502 • gain good overview of networking • detailed knowledge of • physical layer • data link layer • local area networks • elementary protocol specification and analysis • elementary performance analysis

  4. homeworks, etc: CS3502 • homeworks passed out in class OR in electronic form. NOT GRADED. • solutions for majority of homeworks provided. • 3 tests spaced roughly 1/3 of quarter • tests based - in order of priority- on • homeworks • class notes, lectures • text

  5. introduction: CS3502 • network definitions • classifications • models (high level) • ISO model • DOD model • IEEE model • purposes of networks • network industries • communication protocols

  6. Basic Terms - moving information from one physical node to another - data - a pattern of 0’s and 1’s - a physical system for holding information - moving data from one physical node to another - changing data within a node • Communication • Information • Data • Node • Data Communication • Data Processing

  7. Examples of Networks • local, long distance telephone networks • computer LANs: ethernet, token ring • ARPANet/MILNET WANs • Cable TV networks • Cellular phone networks • The INTERNET

  8. network definitions • Networks • computer network • distributed network • LAN, MAN, WAN • integrated network • internetwork/Internet

  9. network classification • geographical coverage (LAN ... WAN) • topology • switching technique • speed (data rates) • data/information content

  10. geographical coverage • LANs • simpler, less software layers • higher data transfer rates (generally) • simple routing • IEEE standards • easily connected together via bridges • examples: ethernet, token ring, FDDI

  11. geographical coverage • MANs • traditional category • cable TV, local phone • DQDB, FDDI (?) • less used, as most networks can be classified into LAN/WAN

  12. geographical coverage • WANs • data speeds slower, in general (this distinction fading) • national, international boundaries • includes internetworking • ARPANet first example • much more complex software • OSI model

  13. network topologies • star • ring • bus • fully connected • tree • mesh

  14. switching techniques • broadcast • no switching or routing; 1 station transmits, all others can receive • collisions occur if more than 1 attempts to transmit at once • examples: ethernet LAN and radio networks, satellites (to some degree)

  15. switching techniques • circuit switching • 3 distinct phases • traditional voice network • nice for user, but inefficient use of transmission facilities • served traditional voice networks well, but gradually becoming outdated by new technology

  16. switching techniques • message switching • sends entire message as single transmission • efficiency problems from unbound msg. size • packet switching • fixed packet size • much more efficient use of facilities • several refinements; fast packet switching (ATM) is culmination

  17. network model: ISO 7-layers • designed ~1970; still heavily referenced • 7 layer model for networks -- 1. physical - moves a bit from a to b using a physical(electrical, optical, etc.) signal 2. data link - groups bits into frames, or messages, for error control and information 3. network - routing function

  18. network model: ISO 7-layers 4. transport - end to end; interface between user apps and the network/internet 5. session, presentation - ?? 7. application - user interface to network, and user services: email, file transfer, world wide web, etc.

  19. network model: IEEE LAN model • complements ISO model for LAN specific networks; • more specific in data link, physical layers; other layers unchanged • layers: • physical • MAC: media access control • LLC: logical link control

  20. network model: DoD model • Alternative view; viewed networks as basic building blocks, thus not included in model • Fewer layers • Applications • host-host (transport; now TCP ) • internet layer (now IP) • network interface layer

  21. purposes of networks • resource sharing • increased reliability (redundancy, etc.) • efficiency • communications • future applications: voice, video, data, images, appliances, .... ?

  22. basic network services • e-mail • file transfers (ftp, etc) • remote login (rlogin, telnet) • WWW (web)

  23. network ing industry • historically two separate and very different industries -- computers and communications • computer industry: IBM, DEC, Sun, Apple, Cray, SGI, Compaq, Dell, Gateway, Microsoft, etc • communications: AT&T, Sprint, MCI-WorldCom, RBOCs, GTE, other phone companies, etc.

  24. network ing industry • these 2 industries have been merging • signs of the merging • initial purpose of each • signals • importance of each to the other • research labs • Sun’s logo “the network is the computer”

  25. industry sectors • Computer Industry • mainframes, “big” computers - IBM, Cray • mid-size, workstations - Sun, SGI, (DEC, Tandem) • personal computers (manufacurers) -Compaq, Dell, Gateway • PCs - software - Microsoft • semiconductors for PCs - Intel, AMD, NSM

  26. industry sectors • Communications • long distance telephone (ATT, Sprint) • local telephone (Pacific Bell, etc.) • telecom. equipment (Lucent, Nor. Telecom) • telco eqmt (Lucent, etc.) • data; internet (Cisco, 3Com) • internet service providers (AOL, etc) • radio, wireless data, satelite, etc

  27. standards for networks • reasons for standards • advantages • disadvantages • standards organizations

  28. communication protocols • protocol: the algorithm or procedure used for communication between processes at the same layer • examples: telephone call; e-mail • protocol processes make use of lower layers as a service. • heart of communications process

  29. communication protocols • some things protocols do • bit interpretation to signals • group bits into messages • error detection and correction • synchronization • make more efficient use of networks facilities

  30. communication protocols • three basic phases of data communications 1. connection establishment 2. data transfer 3. connection termination • connection-oriented/connectionless

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