OSI Model and TCP/IP Protocol suite

OSI (Open System Interconnection) OSI model defines a framework of Network.. This is fantastic way to teach about Network. It provides interoperability. Means how protocols and equipments work together.
OSI is industry standard model maintained by ISO (International Standards Organization). OSI is not popular model in enterprise network. We don't use OSI model so we call it reference model to understand the way of sending and receiving information from one system to another system.
 People generally ask what was the purpose of making this kind of model?
There is story behind the OSI reference model.
Once upon a time networking protocol didn't exist. Vendor used to create protocols to make communication between their products. Example - IBM created SNA and Apple created Apple talk. Other vendors also used to create their proprietary protocols model.
So we had vendor to vendor communication but this type of scenerio couldn't make Network large.
We needed something to be in network or a common thing so all vendors could follow and could have communication.
ISO worked on that and gave an OSI model.
Other side DoD gave a protocol suite called TCP/IP. During 1990 Companies started using OSI and TCP/IP in enterprise networks and at the end of the year TCP/IP became popular and OSI fell away.
 In comparison of TCP/IP all models didn't succeeded..
But first we learn OSI model and learn about all the layers and their functionalities.
Benefits of OSI Model -
 1. Easier to Learn about Networking protocols
 2 Multiple Vendor Interoperability
 3.Easier to Identify Network issues
 4. Helps in developing new Networking protocols
 5. It's layered model so each Layer has it's own functionality to perform task