Information and Communication Technology

4.1.5  Network Protocols and Software

When computers use a common channel for data communication, they follow some rules and procedures to prevent any data collisions. These procedures (a set of standards for communication) are called the network protocols. They are similar to traffic rules used to prevent any road accidents.

A protocol is simply an agreement between the communicating parties on how communication is to proceed. Violating the protocol will make the communication more, difficult, if not impossible. Networks normally use a hierarchy of protocols that are implemented using a software called network software or network operating system. Like as, network operating systems control the flow of data between network nodes. Two common protocols used in local area networks are:

• Carrier-sensed multiple access/collision detection (CSMA/CD)
• Token passing

In the CSMA/CD system, a computer that wants to send a message monitors the line continuously and begins to send its message when there is no traffic. In case of collisions, the message is transmitted at the next opportunity.

In the token passing system, a collection of bits called a token is passed in a certain order in the network. The node currently holding the token has the right to send a message over the network. If the node has nothing to send, the token is passed on to the next node in the line. The function of token passing is to prevent multiple nodes from sending messages.

The Internet uses a protocol known as transmission control protocol/internet protocol (TCP/IP) for routing information over the network. Internet protocol incorporates basic rules such as the composition of internet address, the size of the data to be delivered, and so forth. Transmission control protocol ensures the reliability of transmission.