Protocol: Protocol is a software, i.e., set of rules which are used to establish communication between several computers. It defines the exact order in which two machines exchange data with one another. Protocols are technical customs or guidelines that govern the exchange of signal transmission and reception between equipment. Each protocol specifies the exact order in which signals will be transferred. Both Hardware and software are designed to handle specific protocols. Functions of Protocol: There are the following functions of protocol:

• How to begin and terminate a session between two computers?
• How the messages in a session are to be framed?
• How errors in the transmission of messages are to be detected?
• How messages are to be retransmitted when errors are detected?
• How to find out which message block was sent by which terminal computer and to whom?
• How the dialogue on the communication line proceeds?

Examples:

1. TCP/IP (Transmission Control Protocol/Internet Protocol): TCP breaks up the data to be sent into packets. It guarantees that any data sent to the destination computer reaches it. IP is a set of conventions used to send packets from one host to another. It is responsible for routing the packets to a desired destination IP address.

2. X.12: This protocol is used to establish a connection between companies to exchange important papers.

3. X. 25: This protocol establishes the interface for common data network.

4. HTTP: HyperText Transfer Protocol works on the internet to send or receive files from different locations.