Network Protocols: OSI and TCP/IP

In order to meet the challenges of multi-vendor devices on a network and to break the complexity of computer communications, there are two types of networking models that are developed based on the layered protocol approach:

1. OSI (Open Systems Interconnection): A 7-layer model.
2. TCP/IP (Transmission Control Protocol/Internet Protocol): A 4-layer model.

Some of the layers of both models overlap, as we shall see.

---

OSI (Open Systems Interconnection) was developed by ISO, the International Organization for Standardization and ITU-T, the International Telecommunication Union Standardization Sector, in 1982.

This model divides the complex computer communication into seven distinct layers, with each layer having its own specific functions and protocols. Each of the layers extends services to the layer directly above it and is given services from the layer directly below it. Hence all the seven layers together bring about the communication between the devices in a network.