Protocol

A protocol means the rules that are applicable for a network. Protocol defines standardized formats for data packets, techniques for detecting and correcting errors and so on.
To understand the concept of a communication protocol, let us assume that A and B need to talk to one another. They want to exchange their ideas. But it turns out that, both, A and B are egoists. They start talking again simultaneously, then pause for breath simultaneously, and then start talking again. Now imagine the confusion and chaos. To avoid it, they must follow a set of rules while talking. For instance, say first A must talk, then he/she must give B a chance to put forward his/her ideas, and so on. This common set of rules would be known zz communication protocol for A and B.
Thus for effective use of a network it must follow a standardized protocol. There are various protocols that are used in various types of networks. For example, IBM LAN software, DEC net (Digital’s family of communication protocols), TCP/IP (Transmission Control Protocol/Internet Protocol) etc.