OSI reference model

The OSI Reference Model

by Networking Guy


When the internet started evolving, a common standard for the protocols were required. The ISO (International Standards Organization) put forward the idea of the OSI model. It was decided that this reference model will be called ISO OSI (Open Systems Interconnect) because it dealt with connecting open systems. When we deal with open systems, it does not mean systems that are free or open source or even have security issues. It is just a term coined for computers that communicate with each other.

Principles involved in designing the OSI Reference Model

This reference model was created after considering certain requirements on a computer network. Here are those requirements

  1. There must be a specific, well defined function for each of the layer in the OSI reference model
  2. There must be minimum flow of information between these layers. Hence the number of layers chosen must be so that the flow of information is limited and quick
  3. Each layer must provide a different level of abstraction
  4. The internationally defined protocols must be considered while defining the layers that they will work on in the osi reference model
  5. Even though point #2 implies create more layers, a layer should only be created when it is needed and not for the sake of another layer.

Layers in the OSI model

I have written detailed individual articles on each of these layers for your easy reference. Please click on these links about the various layers of the OSI reference model and go through them individually.

  1. Application Layer
  2. Presentation Layer
  3. Session Layer
  4. Transport Layer
  5. Network Layer
  6. Data Link Layer
  7. Physical Layer

One must never confuse the reference model with a network architecture. The OSI model just gives a “what each layer must do” information and not how they are done.