OSI is an abbreviation for Open Systems Interconnection. A model for OSI (implying that equipment from any manufacturer can be connected to any other manufacturer’s equipment).
-This is the highest level,closest to the user.
-It supports the transfer of information between end-users, applications programs and devices.
-Several types of protocol exist in this layer, covering specific and general applications such as accounting, entry control and user identification.
-It is the user’s interface into the network.
-When a user requests a particular service from the network, the session layer handles the dialogue.
-It handles the data transmission between host computers.
-Dealing with addressing and error controls to ensure a high quality data transmission service for the network.
-The function of the network layer is to perform the routing of information around the network.
-Connecting adjacent nodes in the network.
-Carrying out accounting functions to enable the network owner to charge users.
Data link layer
-The physical data transmission media used in a network are subjected to interference which can corrupt data, and this layer handles data transmission errors.
-The techniques used for receipt and acknowledgment of data by a receiver are handled in this layer
-This layer is concerned with standards for the mechanical, electrical and procedural aspects of interface devices; for example, the number of pins a network connector should have.
-It is concerned with how the binary data is transmitted along the communication channel.