Stack

The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. The terms are often used interchangeably; strictly speaking, the suite is the definition of the Communications protocols, and the stack is the software implementation of them.

Individual protocols within a suite are often designed with a single purpose in mind. This modularization makes design and evaluation easier. Because each protocol module usually communicates with two others, they are commonly imagined as layers in a stack of protocols. The lowest protocol always deals with low-level interaction with the communications hardware. Every higher layer adds more features and capability. User applications usually deal only with the topmost layers (see also OSI model)\