In networking, protocols are layered on top of each other, with each layer being responsible for a different aspect of communication. A protocol stack is a particular software implementation of a computer network protocol suite. The suite consists of the protocol definitions, whereas the stack is the software implementation.

Protocols within a suite are designed with a very specific purpose, and each protocol typically communicates with two others in the stack. The lowest protocol deals with the low-level physical interaction of hardware, whereas user applications deal with only the uppermost layers. Protocol stacks are generally divided into three parts dealing with applications, transport, and media.

See Also: Encapsulation; Network; OSI-Model; Protocol.