1.2 Computer Protocols

For different entities in a system to communicate successfully, they must understand the same language.

This is in analogy to human communication where a common language (protocol) must exist to enable people to communicate.

Figure 1.2 illustrates how two persons follow a certain protocol in a conversation:

		Such protocol starts with a greeting by one side of the conversation.
		A greeting reply from the other person indicates his/her acceptance to be engaged in the conversation.
		Other exchange of messages could then follow.

Note that:

		The two persons in the conversation need to use specific messages and
		That the conversation should be constructed from a specific order of messages for the human communication to be achieved.

A computer communication protocol represents such common language required to achieve communication between entities in a data communication system.

1.2 Computer Protocols

A computer protocol defines a set of rules that govern the communication process between communicating entities including:

		The types of messages exchanged between communicating entities.
		The format of such messages.
		The order at which messages are exchanged.

A computer protocol can also define:

How data is split into sequenced chunks if required for communication.

Data flow and error handling mechanisms can also be defined in a computer protocol for speed matching between computers in addition to providing delivery guarantees of data communicated.

1.2 Computer Protocols

Figure 1.2: Computer Protocol Human Analogy