<P> In telecommunication, a communication protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity . The protocol defines the rules syntax, semantics and synchronization of communication and possible error recovery methods . Protocols may be implemented by hardware, software, or a combination of both . </P> <P> Communicating systems use well - defined formats (protocol) for exchanging various messages . Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation . The specified behavior is typically independent of how it is to be implemented . Communication protocols have to be agreed upon by the parties involved . To reach agreement, a protocol may be developed into a technical standard . A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communication what programming languages are to computations . </P>

What aspects of network communication are described by a protocol