THE OSI REFERENCE MODEL

Introduction:

OSI stands for Open System Interconnection and is a standard reference model for communication between two end user in a network.

Featurs of OSI modal:

The Osi madal is not a protocol,It is a modlfor understanding and designing a network architecture that is flexible,robust and interoperable.

OSI layer consists of seven layer and these layers are in two groups.

one group is consist of four upper layer(layer 4 to 7) which are Application, Presntation, Session, Transport.

The upper layer are used whenever a message passes from or to a user.

The other group is consists of lower three layer (layer 1 to 3) which are Network, Datalink, Physical.

The lower layer are used whe any message passes through the host computer.

Messages intended for this computer pass the upper layer.

Message destined for some other host are not passed up to the upper layer but are forwarded to another host.'