Networking / Beginners

Models and Protocols

It is easy to confuse the OSI and Internet models with the OSI and Internet protocols. A model is a set of guidelines on how one should go about designing a network protocol. For example, it can say 'use a physical layer which will deal with voltages, frequencies, etc.'. The model does not say 'use copper wire and voltages of 5 V representing 1 bit'. That is a specific protocol implementation.

A model can have many implementations that fit it. For example, consider the following network: two plastic cups joined by a piece of string. The physical layer is the cups and string; the network layer is empty; the transport layer is saying 'over' at the end of each voice packet; the application layer is whatever we are talking about. This is a network implementation that fits the Internet model.

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In this tutorial:

  1. Layering Models
  2. The Seven Layer Model
  3. The Physical Layer
  4. The Data Link Layer
  5. The Network Layer
  6. The Transport Layer
  7. The Session Layer
  8. The Presentation Layer
  9. The Application Layer
  10. How the Layers Fit Together
  11. Why Layers and Encapsulation?
  12. The Internet Model
  13. The Link Layer
  14. Models and Protocols
  15. Comparing OSI and Internet Models