What is a communication protocol ? What is its role in a network ?

A communication protocol is a formal description of message formats and the rules that two or more machines must follow to exchange those messages.

The reason that the Internet works at all is that every computer connected to it uses the same set of rules for communication. The communication protocol used by Internet is TCP/IP.

1. The TCP or Transmission Control Protocol is responsible for dividing the­ file/message into packets on the source computer. It is also responsible for reassembling the received packets at the destination or recipient computer.
2. The IP or Internet Protocol is responsible for handling the address of destination computer so that each packet is routed (sent) to its proper destination.