1. Layered Architecture

Data Communication & Networking 3rd Semester

Uses separate functional layers Transparent implementation

OSI Model

Stands for Open Systems Interconnection Provides communication regardless of underlying architecture

Has 7 Layers with well defined functions, Boundaries make sure there’s minimum information flow across layers.

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Physical Layer

  • Consists of cables, connectors, wireless radio transceivers
  • Accepts raw string of bits and transmit it across
  • Functions
    • Encoding and signaling
    • Data transmission and reception
    • Topology and physical network design
  • Provides error-free transmission across single link
  • Functions
    • Data framing
    • Error detection and handling
    • Flow Control
    • Addressing - hardware level

Network Layer

  • Deliver packets (Datagrams) from sender to receiver across a network
  • Shield higher layers from details of how packets got to their destination
  • Function
    • Logical addressing
    • Routing
    • Datagram encapsulation
    • Congestion control
    • Quality of service

Transport layer

  • Provide end to end delivery from one host to the other
  • Functions
    • Connection establishment
    • Multiplexing and Demultiplexing
    • Error detection and correction
    • Flow control
    • Quality of Service

Session Layer

  • Provides a means of controlling the dialog between two end users
  • Functions
    • Dialog control (Full vs Half Duplex)
    • Token management
    • Synchronization
    • Recovery management

Presentation Layer

  • Formatting data for transmission
  • Functions
    • Translation
    • Compression
    • Encryption

Application Layer

  • Provides network-based applications to users
  • Ex:
    • File transfer
    • Email
    • World Wide Web