Protocol

A protocol is a set of guidelines or outlines on how communication should occur between two or more computers. Some protocols carry other protocols and these usually fit inside the OSI layer model. Protocols that are carried over IP are defined in /etc/protocols and should not be edited since a certain C library function reads this file for the function getprotobyname() as an example.

Any protocol that is used on the Internet is defined as a standard in the rfc's. There is some proprietary protocols that use Internet protocols for distribution, these are hardly found in the RFC collection and should be avoided when possible.