Data and Computer Networks.ppt
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Data and Computer Networks.ppt Data and Computer Networks.ppt Presentation Transcript

  • 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
      • local area networks
    • elementary protocol specification and analysis
    • elementary performance analysis
  • 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
  • introduction: CS3502
    • network definitions
    • classifications
    • models (high level)
      • ISO model
      • DOD model
      • IEEE model
    • purposes of networks
    • network industries
    • communication protocols
  • Basic Terms
    • Communication
    • Information
    • Data
    • Node
    • Data Communication
    • Data Processing
    - 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
  • Examples of Networks
    • local, long distance telephone networks
    • computer LANs: ethernet, token ring
    • ARPANet/MILNET WANs
    • Cable TV networks
    • Cellular phone networks
    • The INTERNET
  • network definitions
    • Networks
    • computer network
    • distributed network
    • LAN, MAN, WAN
    • integrated network
    • internetwork/Internet
  • network classification
    • geographical coverage (LAN ... WAN)
    • topology
    • switching technique
    • speed (data rates)
    • data/information content
  • 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
  • geographical coverage
    • MANs
      • traditional category
      • cable TV, local phone
      • DQDB, FDDI (?)
      • less used, as most networks can be classified into LAN/WAN
  • 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
  • network topologies
      • star
      • ring
      • bus
      • fully connected
      • tree
      • mesh
  • 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)
  • 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
  • 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
  • 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
  • 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.
  • 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
  • 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
  • purposes of networks
    • resource sharing
    • increased reliability (redundancy, etc.)
    • efficiency
    • communications
    • future applications: voice, video, data, images, appliances, .... ?
  • basic network services
    • e-mail
    • file transfers (ftp, etc)
    • remote login (rlogin, telnet)
    • WWW (web)
  • 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.
  • 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”
  • 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
  • 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
  • standards for networks
    • reasons for standards
    • advantages
    • disadvantages
    • standards organizations
  • 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
  • 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
  • communication protocols
    • three basic phases of data communications
    • 1. connection establishment
    • 2. data transfer
    • 3. connection termination
    • connection-oriented/connectionless