The
software and/or
hardware environment of
two or more communications devices or computers in which a
particular
network protocol operates. A network
connection may be thought of as a set of more or less
independent protocols, each in a different layer or level.
The lowest layer governs direct host-to-host communication
between the hardware at different hosts; the highest consists
of user application programs. Each layer uses the layer
beneath it and provides a service for the layer above. Each
networking component hardware or software on one host uses
protocols appropriate to its layer to communicate with the
corresponding component (its "peer") on another host. Such
layered protocols are sometimes known as peer-to-peer
protocols.
The advantages of layered protocols is that the methods of
passing information from one layer to another are specified
clearly as part of the
protocol suite, and changes within a
protocol layer are prevented from affecting the other layers.
This greatly simplifies the task of designing and maintaining
communication systems.
Examples of layered protocols are
TCP/IP's five layer
protocol stack and the
OSI seven layer model.