TCP/IP Model & Comparison with OSI Reference Model.

The Internet runs over TCP/IP, The Transmission Control Protocol/Internet Protocol, which is actually a suite of protocols, each performing a particular role to let computers speak the same language. TCP/IP was designed by the Defense Advanced Research Projects Agency (DARPA) in the 1970s—the design goal being to let dissimilar computers freely communicate, regardless of location. Most early TCP/IP work was done on Unix computers and now, TCP/IP is the de facto standard that unifies the Internet.

The OSI Reference Model and TCP/IP protocol suites were developed around the same time, and both of them had a model describing network communication. The OSI model is primarily used because of the amount of detail it provides. TCP/IP Model has four abstract layers, and focuses on layers 3 and 4 of the OSI reference model; the TCP/IP model groups the top three OSI layers into a single “Application” layer. This is because these functions typically occur before the data leaves the application itself. Also, because the Data Link and Physical layers of the OSI model are so closely related together, the TCP/IP model groups them into a single “Network Interface” layer. TCP/IP’s goal is to move messages through virtually any LAN product to set up a connection running virtually any network application. 

The graphic below compares both network models.

TCP/IP’s four abstract layers include:

Network interface: This allows TCP/IP to interact with all modern network technologies by complying with the OSI model.

• Internet: This defines how IP directs messages through routers over internetworks such as the Internet.
• Transport: This defines the mechanics of how messages are exchanged between computers.
• Application: This defines network applications to perform tasks such as file transfer, e-mail, and other useful functions.