Internetworking

Communication between two networks or two types of networks or end equipment. This may or may not involve a difference in signaling or protocol elements supported. In the narrower sense - to join local area networks together. This way users can get access to other files, databases and applications. Bridges ad routers are the devices which typically accomplish the task of joining LANs. Internetworking may be done with cables - joining LANs together in the same building, for example. Or it may be done with telecommunications circuits - joining LANs together across the globe.

Two architectural models are commonly used to describe the protocols and methods used in internetworking. The Open System Interconnection (OSI) reference model provides a rigorous description for layering protocol functions from the underlying hardware to the software interface concepts in user applications. Internetworking is implemented in Layer 3 (Network Layer) of the model.

The Internet Protocol Suite, also called the TCP/IP model, of the Internet was not designed to conform to this model. Despite similar appearance as a layered model, it uses a much less rigorous, loosely defined architecture that concerns itself only with the higher level aspects of networking, i.e. it does not discuss hardware-specific low-level interfaces, other than assuming availability of a link-layer interface to the local network link. Internetworking is facilitated by the protocols of its Internet Layer.