· Accept a row of bits and deliver it across a link.
· Deal with a mechanical and electrical interface of the tranmisson media.
· Defines the functions and procedures that the physical device have to perform for transmission to occour.
Major duties :
1. connection establishment and termination of network connections.
2. Defines the characteristics of the interface between the device and the transmission medium.Also defines the transmission medium.
3. Representation and encoding of bits; Binary bits(1 & 0) (and encode into signals; anelog or optical.The layer defines this.)
4. Transmission of bits; Data rate is defined,thus the bit duration is defined.
5. Synchronization; the transmitter and receiver must use the same data rate and their clocks must be synchronized.
6. Reapting or amplification to extend range of transmission.
