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Networks

The OSI seven-layer model

  • 3 things to know
  • A2 Unit 1

Overview

Purpose of the Open Systems Interconnection model, function of the physical layer and function of the data link layer.

What you need to know

Answer each one before you reveal it.

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Key term

State the function of the physical layer.

Key term

State the function of the session layer.

Key term

Name the seven layers of the OSI model in order from the lowest to the highest.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the purpose of the Open Systems Interconnection model?

    Model answer

    The Open Systems Interconnection model is a reference framework that divides network communication into seven layers, so that the functions can be described, designed and troubleshot independently of any particular manufacturer's equipment.

  2. 2

    Name the seven layers of the OSI model in order from the lowest to the highest.

    Model answer

    The seven layers are physical, data link, network, transport, session, presentation and application.

  3. 3

    State the function of the physical layer.

    Model answer

    The physical layer transmits raw bits over the medium, defining the voltages, light pulses or radio signals used, the connector shapes and the bit timing.

  4. 4

    State the function of the data link layer.

    Model answer

    The data link layer packages bits into frames for delivery across one link, adds the hardware addresses of the sender and receiver, and checks each frame for transmission errors.

  5. 5

    State the function of the network layer.

    Model answer

    The network layer adds logical addresses and chooses a route, so that a packet can be forwarded across several joined networks to reach a destination that is not on the local link.

  6. 6

    State the function of the transport layer.

    Model answer

    The transport layer splits a message into segments and rebuilds it at the far end, and provides end-to-end delivery services such as acknowledgement, retransmission and flow control.

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