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OSI Model


OSI Model consists of 7 layers in total, respective names of which are depicted in diagram given below along with their respective positions as Outward and Inward Layers

OSI Model is a Linkage Framework of these seven layers each of which has a distinct role and authority area e.g. Network, Data Linking, User Interface etc. 
OSI Layers

Significance of each of these seven Layers has been explained below--

  1. Layer 1 – Physical Layer :
    • Hardware Layer
    • Specifies Mechanical as well as Electromagnetic features of communication between devices and transmission
    • Network Topology is part of this Layer
  2. Layer 2 – Data Link Layer :
    • Hardware Layer
    • Specifies “Channel Access Control Method”
    • Ensures reliable data transfer through transmission medium
  3. Layer 3 – Network Layer :
    • Makes a choice of Physical Route of transmission
    • Creates a Virtual Circuit for upper  layers
    • Establishes, Maintains & Terminates connections between nodes and ensures proper routing of Data
  4. Layer 4 – Transport Layer :
    • Ensures reliable transfer of Data between User Processes, Assembles & Disassembles  message packets
    • Provides Error Recovery and Flow Control
    • Multiplexing & Encryption are undertaken at this Layer Level
  5. Layer 5 – Session Layer :
    • Establishes, Maintains & Terminates “Sessions” or what we can say “Dialogues” between user processes
    • Identification & Authentication are undertaken at this Layer
  6. Layer 6 – Presentation Layer :
    • Controls “On Screen” display of Data and transforms data to a Standard Application Interface
    • Encryption, Data Compression can also be undertaken at this Layer Level
  7. Layer 7 – Application Layer :
    • Provides User services such as File Transfer, File Sharing etc.
    • Database Concurrency & Deadlock Situation Controls are undertaken at this Layer Level


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