DATA AND COMPUTER COMMUNICATION

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DATA AND COMPUTER COMMUNICATION

• Simplified Communication Model
• source data generation
• transmitter encoding, control (error, speed,
  bandwidth)
• transmission system network
• single processor, multiple processor, local
  network, metropolitan network, long-haul network
• receiver decoding, control
• destination receives data

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• receiver decoding, control
• destination receives data

source transmitter transmission
system receiver destination
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Data Communications

• data transmission
• signal transformation between transmitter and
  receiver
• transmission media
• physical path between transmitter and receiver
• data encoding
• conversion from data to signal
• interface
• asynchronous, synchronous transmission
• pin assignment
• data link control
• flow, error control
• multiplexing
• channel, network utilization

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Data Communications Networking

• Wide-Area Networks
• circuit switching network
• dedicated communications path between two
  stations using internal switches (physical link).
  ex) telephone network
• packet switching
• data is stored in a packet
• mainly used for computer communications
• data rate 64kbps
• frame relay
• low error rates (less control for error) with
  modern high-speed telecommunication system
• high data rates 2Mbps
• ATM (asynchronous transfer mode)
• cell relay

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Example 1

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Example 2

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ATM (Asynchronous Transfer Mode)

• evolution from frame relay and circuit switching
• fixed size packet (cell)
• less processing overhead
• high speed 10 100 Mbps
• virtual channel with dynamic data rate
• ISDN (integrated services digital network)
• worldwide public telecommunications network
• narrowband ISDN (1st generation)
• circuit switching with 64 kbps channel
• frame relay
• broadband ISDN (2nd generation)
• based on packet switching network
• ATM development in ISDN (on-going research)

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Local Area Networks

• range a building or a cluster of buildings
• normally owned by same organization
• higher data transfer rate
• recently ATM LANS in fibre channel

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Protocols and Protocol Architecture

• protocol a set of rules governing exchange of
  data between two entities
• key elements in protocol
• syntax data format
• semantics control information for coordination
  and error handling
• timing speed matching and sequencing
• Simplified Architecture for File Transfer
• path activation, destination ready to receive,
  file management ready to receive, same file format

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Three Layer Model

• application layer
• transport layer sequencing, error control
• network access layer

Protocol Architectures and Networks
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Operation of protocol architecture

• Transport protocol header may include
• destination SAP (DSAP)
• sequence number (sending more than one data)
• error-detection code
• Network access protocol header may include
• destination computer address (destination host)
• facilities request priority bit

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TCP/IP Protocol Architecture

• most widely used operable architecture
• based on packet-switched network ARPANET
• 5 layers
• Application layer support user application
• Transport layer transmission control protocol
  (TCP) provides reliability of exchanging data
• Internet layer internet protocol (IP) provides
  routing function across multiple networks
• Network access layer circuit switching, packet
  switching (e.g., X.25), local area network
  (Ethernet)
• Physical layer physical interface between
  devices and a transmission medium or network

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OSI (open systems interconnection) Model

• 7 layers developed by International
  Organization for Standardization (ISO)
• Application provides access to OSI environment
  for users and also provides distributed
  information
• Presentation provides application processes from
  data representation (syntax)
• Session provides the control structure for
  communication between applications
• Transport provides reliable, transparent
  transfer of data between end points (error
  recovery, flow control)
• Network provides data transmission and switching
  techniques to connect systems
• Data link provides for the reliable transfer of
  information across physical link
• Physical transmission of unstructured bit stream
  over physical medium

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Comparison between TCP/IP and OSI

• Many OSI based protocols are developed
• However, TCP/IP dominates over OSI
• Protocol Architecture