Network Protocols

A network protocol is a set of rules for exchanging information over a network. Protocols are to networks what language is to humans. For two devices on a network to successfully communicate with each other, they must both follow the same protocols.

A networking system is designed as a multi-layer system, where each layer has its protocol for managing and transmitting data. The Open Systems Interconnection (OSI) model is a conceptual model used to define seven such layers. Without getting into details of all layers, just to illustrate the concept, the uppermost layer is known as the Application layer, whereas the lowermost layer is known as the Physical layer. The Application layer is the actual software application that initiates the sending of the data and on the receiving side is the final application that consumes the data. This Physical layer is the core layer at which transmission across a medium takes place. The five layers manage everything required to transform the data from the format application sends it into the format the physical medium can transmit it in.

Each protocol defines the rules for computers to interact at that level and leverages the services of the protocol layer below it until the lowest layer controls the hardware that sends information across the transmission media.

The two most widely used protocols at the lower layers are the Transmission Control Protocol (TCP) and Internet Protocol (IP), together known as TCP/IP.

The widely used application protocols are HyperText Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), and File Transfer Protocol (FTP).