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OSI Layers

Published: Jun 24, 2019

Last updated: Jun 24, 2019

    A quick and dirty on the seven layers of the OSI Model.

    OSI Layers in Network Traffic

    Layer 1: Physical

    Represents the bit-level transmission between network nodes over the connection medium.

    Data: Bits across the wire (1s and 0s) as pulse of electricity or light.

    Layer 2: Data Link

    Data Link Layer handles communications between adjacents network nodes via physical addressing (MAC).

    Data: Frames.

    Layer 3: Network

    Handles routing messages (packets) via the best route to reach its destination based on IP address.

    Data: Packets.

    Layer 4: Transport

    Defines how data will be sent providing validation and security.

    Data: Segments.

    Layer 5-7: Application, Presentation, Session

    Layers 5-7 are typically managed by the application itself, providing the interface for the user to communicate.

    Data: Data.

    Data in a TCP/IP Example

    • Data Link Layer (2): Frame = Frame Header + Frame Data
    • Network Layer (3): Packet = IP Header + IP Data
    • Transport Layer (4): Segment = TCP Header + Application Data
    • Application Layer (5-7): Data = App Header + User Data

    When dealing with subnetting, network masks etc, note that you are working in the Network Layer (layer 3).

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    Dennis O'Keeffe

    • Melbourne, Australia

    Hi, I am a professional Software Engineer. Formerly of Culture Amp, UsabilityHub, Present Company and NightGuru.
    I am currently working on Visibuild.


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    OSI Layers


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