Network Protocol Hierarchy Definition

To reduce their design complexity, most networks are organized as a series of layers or levels, each one built upon the on below it. The number of layers, the name of each layer, the contents of each layer, and the function of each layer differ from network to network. However, in all networks, the purpose of each layer is to offer certain services to the higher layers, shielding those layers from the details of how the offered services are actually implemented.

Layer n on one machine carries on a conversation with layer n on another machine. The rules and conventions used in this conversation are collectively known as the layer n protocol. Basically, a protocol is an agreement between the communicating parties on how communication is to proceed. As an analogy, when a woman is introduce to a man, she may choose to stick our her hand. He, in turn, may decide to shake it or kiss it, depending, for example, on whether she is an American lawyer at a business meeting or a European princess at a formal ball. Violating the protocol will make communication more difficult, if not impossible.

Below the bottommost layer is the physical layer through which actual communication occurs. Between each pair of adjacent layers there is an interface. And finally, a set of layers and protocols is called a network architecture.

Related Terms

• Local Area Network
• Wide Area Network

Other Definitions

References
Computer Networks by Andrew S. Tanenbaum