- It divides the stream of bits into small manageable packets called as frames.
- The data link layer transforms the physical layer, a raw transmission facility, to a link responsible for node-to-node (hop-to-hop) communication.
- It provides Hop-Hop connection.
- Access control
- Error control
- Flow control
- Physical addressing.
Taking streams of bits from the network layer and divides into small manageable units is called frames.
A large stream of bits can be sent throughout the channel but doing so will have some issues like :
When an error occurred, you have to check the entire message and then retransmit the whole bitstream. When a message is carried in one very large frame, even a single-bit error would require the retransmission of the whole message. When a message is divided into smaller frames, a single-bit error affects only that small frame.
SFD (Start frame delimiter):- It tells the start of the frame.
EFD(End frame delimiter):- these bit tells End of the frame.
Types of framing:-
1. Fixed-size Framing:
Size of each frame is fixed. Here we don't need any delimiter because the size of frames is confirmed and it itself acts as the delimiter.
2. Variable Size Framing:-
Here we have to define delimiter. We have to tell the beginning and end of each frame. For this, we have two approaches.
Character Stuffing and Bit Stuffing.