OSI Reference Model

OSI stands for Open Systems Interconnection. It is a Networking Reference Model that was created by the ISO (International Organization for Standardization), sometime in the late 1970s.

How & Why did the OSI Model come into existence?

When people started waking up to the benefits of networking, the options to buy hardware were very limited because, at that time, hardware of one manufacturer could not work with hardware of a different manufacturer.This model was created so that hardware and software of different manufacturers and vendors could work together, using common Networking Protocols.

The OSI Model tells us how data and network related information is sent from an application on one computer, through the network to an application on another computer.The OSI Model has a Layered and Heirarchical approach to Networking.

The OSI Model is a Framework which provides a set of guidelines to create and implement Networking Standards, Networking Devices and Internetworking Schemes.

The Different Layers of the OSI Model:

The OSI Model has Seven Layers. Before I tell you what the layers are, I want you to remember the phrase:

Please Do Not Take Sales Person’s Advice

(Please note: I don’t mean any disrespect to Sales People. This is just an easy way to remember the different layers!)

In the above phrase, note the First Letters of Each Word – they stand for the different Networking Layers – which are as given below:

  • APPLICATION LAYER
  • PRESENTATION LAYER
  • SESSION LAYER
  • TRANSPORT LAYER
  • NETWORK LAYER
  • DATA LINK LAYER
  • PHYSICAL LAYER
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