A communication protocol may be a system of rules that allow two or more entities of a communications system to transmit information via any quite variation of a physical quantity. The protocol defines the principles , syntax, semantics and synchronization of communication and possible error recovery methods. Protocols could also be implemented by hardware, software, or a mixture of both. [failed verification] Communicating systems use well-defined formats for exchanging various messages. Each message has a particular meaning intended to elicit a response from a variety of possible responses pre-determined for that specific situation. the required behavior is usually independent of how it's to be implemented. Communication protocols need to be prescribed by the parties involved. to succeed in an agreement, a protocol could also be developed into a technical standard. A programing language describes an equivalent for computations, so there's an in depth analogy between protocols and programming languages: protocols are to communication what programming languages are to computations. An alternate formulation states that protocols are to communication what algorithms are to computation.