Network Basic

OSI Reference model

The OSI reference model has 7 layers.

*The physical layer

* Data link layer

*Network layer

*Transport layer

*Session layer

*Presentation layer

* Application layer

Each layer is defined for having associated with distinct functions. The functions performed by each layer can be described as below.

*The Physical layer: The layer defines the electrical and mechanical aspects of interfacing to a physical medium for transmitting dat. It also defines how physical links are setup, maintained and disconnected.

*The data link layer: This layer establishes an error free communication path between computers over the physical channel. It gives the standard for framing messages, checking integrity of messages received, accessing and using channels and sequencing of transmitted data.

*The Network layer: This layer determines the setting up of a logical path between computers in a network, message addressing to computers  and controlling message flow between computer nodes.

*The Transport layer: Once a path is established between computers it provides control standards for a communication session for enabling processes to exchange data reliably and sequentially, independent of which systems are communicating or their location in the network.

*The Presentation layer: This layer provides facilities to convert encoded transmitted data into forms which can displayed on a video terminal or printed.

*The Application layer: This layer provides services that directly support users such as file transfers, remote file access data base management etc,,