OSI MODEL

OSI MODEL

LAYER 1 - Physical - The physical layer, the lowest layer of the OSI model, is concerned with the transmission and reception of the unstructured raw bit stream over a physical medium. It describes the electrical/optical, mechanical, and functional interfaces to the physical medium, and carries the signals for all of the higher layers
1. Physical Medium Attachment
  1. Data Encoding
    1. Physical Medium Transmission
LAYER 2 - Data Link - The data link layer provides error-free transfer of data frames from one node to another over the physical layer, allowing layers above it to assume virtually error-free transmission over the link
1. Frame Sequecing
  1. Frame acknowledgment
    1. Frame error checking
      1. Frame traffic control
LAYER 3 -Network - The network layer controls the operation of the subnet, deciding which physical path the data should take based on network conditions, priority of service, and other factors
1. Routing
  1. Frame fragmentation
    1. Logical-physical address mapping
      1. Packets
LAYER 4 - Transport - The transport layer ensures that messages are delivered error-free, in sequence, and with no losses or duplications. It relieves the higher layer protocols from any concern with the transfer of data between them and their peers
1. Message segmentation
  1. Message acknowledgment (TCP, UDP)
    1. Message traffic control
      1. Session multiplexing
LAYER 5 - Session - The session layer allows session establishment between processes running on different stations
1. Session establishment, maintenance and termination
  1. Session support
LAYER 6 - Presentation - The presentation layer formats the data to be presented to the application layer. It can be viewed as the translator for the network. This layer may translate data from a format used by the application layer into a common format at the sending station, then translate the common format to a format known to the application layer at the receiving station
1. Character code translation
  1. Data conversion
    1. Data compression
      1. Data encryption
LAYER 7 - Application - The application layer serves as the window for users and application processes to access network services
1. Resource sharing and device redirection
  1. Remote file access
    1. Remote printer access
      1. Electronic messaging (such as mail)
        Network management

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	Created by Tobi_Adekunle almost 11 years ago