OSI  stands for Open System Interconnection  . OSI is standard reference model for network communications system , which has been accepted by the all the computer and telecommunication system organisation  .

OSI was introduced in 1983 by representatives of the major computer and telecom companies and was adopted by ISO as an international standard in 1984.

It consists of the seven layers where each layer performs a specific function for the communication over the network. 

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

The OSI model helps standardize networking protocols and fosters interoperability between different systems and technologies.