Importance Of Flow And Error Control:
The most important function of the data link layer is to provide flow control and error control mechanisms. In data communication it requires, when two devices working together, one device for sending and other for receiving for correcting errors.
Flow control:
The most important duty of data link layer is flow control coordinates the amount of data can be sent before receiving acknowledgement.
From most protocols, flow control is a set of procedures that tells the sender how much data it can transmit before it must wait for an acknowledgement from the receiver,
Any receiving device has a limited speed at which it can process incoming data and a limited amount of memory in which to store incoming data, the receiving devices must be ready to inform the sending device before those limits are reached and to request that the transmitting device send fewer frames or stop temporarily.
Incoming data must be checked and processed before they will be used. The rate of such processing is usually slower than the speed of transmission. For this reason, each receiving device features a block of memory, called a buffer, reserved for storing incoming data until they’re processed. If the buffer begins to refill, the receiver must be ready to tell the sender to halt transmission until it’s once more ready to receive.
Error control:
Error control is used for the both error detection and error correction. It allows the receiver to tell the sender of any frames lost or damaged in transmission and coordinates the retransmission of these frames by the sender.
The term error control refers primarily to methods of error detection and retransmission in the data link layer.
Anytime a mistake is detected in an exchange, specified frames are retransmitted. This process is called automatic repeat request (ARQ).