Flow control protocols
Flow control is a design issue at the data link layer, it generally observes the proper flow of data from the sender to the receiver. It is essential as the sender can transmit data at a very fast rate. The receiver will be able to receive the information and process it.
It happens only when the receiver has a very high load of traffic as compared to the sender.
Approaches to flow control:
It can be classified into two categories:
- Feedback-based flow control
- Rate-based flow control
Feedback-based flow control
In this technique, the sender simply transmits data to the receiver, and the receiver transmits it back to the sender. It also allows the sender to transmit more amount of data.
Rate-based flow control
In this technique, when the sender sends data at a faster speed to the receiver and the receiver is not able to receive the data at the same speed, then a built-in mechanism in protocol will limit the overall rate at which the data is being transferred.
Flow control techniques in the data link layer (DLL)
There are two techniques for flow control in the DLL, they are as follows:
- Stop-and-Wait Flow Control
- Sliding Window Flow Control
Stop-and-Wait Flow Control
The stop and wait flow control method is the easiest form of flow control. In this method, the message or data is broken into multiple frames, and the receiver indicates its readiness to receive a frame. When the indication is acknowledged then the sender sends frames.
Sliding Window Flow Control
The Sliding Window Flow Control method is used in the ordered delivery of packets or frames. It assumes that none of the other entities tries to communicate until current data or frame transfer gets completed, and the sender transmits frames or packets before receiving any indication.
The sender and the receiver agree on the total number of frames. The DLL uses this method to increase the network throughput as it allows the sender to have more than one unacknowledged packet “in-flight” at a time.