Protocols

All communications software use protocols, sets of semantical and syntactical rules that determine the behavior of functional units in achieving communication.

Protocols define how information is delivered, how it is enclosed to reach its destination safely, and what path it follows. Protocols also coordinate the flow of messages and their acknowledgments.

Protocols exist at different levels within the kernel and cannot be manipulated directly. However, they are manipulated indirectly by what the user chooses to do at the application programming interface (API) level. The choices a user makes when invoking file transfer, remote login, or terminal emulation programs define the protocols used in the execution of those programs.