Protocol Stack

The terms protocol stack are often used interchangeably. In general, protocol defines the suite while the stack defines their program implementation. Individual protocols within a suite are usually designed with a sole purpose in mind. This modular structure adds ease to the tasks of operation and evaluation. Since each protocol module typically communicates with others, they are often thought of as layers in a stack of protocols. The low-level protocol is intended to deal with the physical interaction of hardware devices. The purpose of higher levels is to implement greater features. Protocol stacks are usually divided into three major sections in practical implementation: media, transport and applications. A given operating system may have two well defined interfaces intended for software use: one interface between the media and transport layers, and another interface between transport and application layers. The media-to-transport interface specifies how a transport protocol program makes use of certain media and hardware devices. For instance, this level would define how a TCP/IP program interacts with Ethernet hardware. The application-to-transport interface specifies how software applications make use of transport layers. A defining example would be how a web browser application interacts with a TCP/IP program.