OSI reference model was devised by ISO for effective and smooth creation and functioning of any network.

This model has seven layers.

Physical layer: This layer basically deals with physical, electrical and mechanical specifications of a network model. It accepts raw bit streams and passes it through physical medium to the receiver.

Data link layer: This layer accepts raw bit stream from physical layer and convert it into meaningful information i.e. frames. This layer deals with point to point connection. It also looks after the error control and flow control of the information.

Network layer: This layer basically deals with routing of the information (packets) received from transport layer through either connection oriented virtual circuit or connectionless Datagrams. It also takes care of congestion control mechanism within the network.

Transport layer: The functioning of transport layer is almost similar to data link layer, where data link layer perform point to point connection, transport layer deals with end to end connectivity. It offers connection oriented service to the upper layers.

Session layer: This layer establishes session between sender and receiver before the actual transmission. It makes compatibility between two sources working at different platforms.

Presentation layer: This layer deals with syntax and semantics of the information being transferred. It helps in interoperability of different encoding methods. It also deals with encryption and compression of data.

Application layer: This layer enables the end user to access the network. It provides user interface and support for services such as e-mail, file transfer, remote log in and shared database management etc. Famous protocols used by this layer to offer these services are SMTP, FTP, TELNET, DNS etc.