The English used in this article may not be easy for everybody to understand. (April 2012)
The TCP/IP model (Transmission Control Protocol/Internet Protocol) is a model with four layers which is for both modelling current Internet architecture, as well as providing a set a rules that govern all forms of transmission over a network. DARPA, an agency of the United States Department of Defense,created it in the 1970s. It evolved from ARPANET, which was an early wide area network and a predecessor of the Internet. The TCP/IP Model is sometimes called the Internet Model or less often the DoD Model.
This model was being made at the same time as the OSI Model was created. The TCP/IP model is not the same as the OSI Model, however it was influenced by the model, which is why many names of the different layers are the same.
The TCP/IP model describes a set of general design guidelines and implementations of specific networking protocols to enable computers to communicate over a network. TCP/IP provides end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination. Protocols exist for a variety of different types of communication services between computers.
TCP/IP has four abstraction layers as defined in RFC 1122: link layer, IP layer, transport layer and application layer. People often compare this layer architecture with the seven-layer OSI Reference Model; using terms such as Internet reference model. This is incorrect, however, because it is descriptive while the OSI Reference Model was intended to be prescriptive, hence being a reference model.
The TCP/IP model and related protocols are maintained by the Internet Engineering Task Force (IETF).