Data Link Layer:
It is responsible for node-to-node delivery of data.
It receives the data from network layer and creates FRAMES, add physical address to these frames & pass them to physical layer.
It consist of 2 layers:
Logical Link Layer (LLC).
Medium Access Control (MAC).
Functions of Data Link Layer:
It is used for synchronization and error control for the information.
It divides the bits received from Network layer into frames.
It provides Flow Control.
To enable the error detection, it adds error detection bits to the data which is to be transmitted.
CRC in a trailer(reason):-
1. The Data Link Layer is the second layer of OSI Model.
2. It is responsible for node-to-node delivery of data.
3. It receives the data from network layer and creates FRAMES, add physical address to these frames & pass them to physical layer.
4. Data Link Layer delivers the frames using Hardware Address.
5. The CRC is computed while the packet is being transmitted and then incorporated in a trailer.
6. Similarly, the receiver computes the CRC and compares it with the transmitted one. 7. Thus it is more efficient to put CRC in a trailer. 8. Because only one pass needs to be made over the packet as it computes the CRC while scanning the packet, and then outputs it at the end (trailer). 9. If the CRC were in the header, then two passes would be necessary - one to compute the CRC, and one more to append it to the front of the packet.
10. Therefore using the trailer cuts the work in half.