Introduction to Networking

Flow Control Of Noiseless Channel

For Flow control of Noiseless channels, we assume an ideal channel where no frames are lost, corrupted, or duplicated. Protocols in flow control for Noiseless channels are of following two kinds

1. Simplest Protocol

It is a very simple and easy-to-implement protocol. It is a unidirectional protocol in which data frames travel only from sender to receiver.

In the simplest protocol, the sender sends sequence numbers of frames without thinking about the receiver.  No concept of acknowledgment is used by the receiver.

The following figure explains all

2. Stop and Wait Protocol

In stop and wait, the sender sends one frame and waits for Acknowledgement (feedback) from the receiver. When the Acknowledgement arrives, the sender sends the next frame.

So, it is a half-duplex in direction, as shown in the following figure

The most important thing about stop and wait is that it does not use any timer. If the frame is lost after transmission, then the receiver has to wait for an infinite amount of time.

In the same way, if ACK is lost after transmission, then the sender has to wait for an infinite amount of time.

Note: If the speed of the sender is higher than that of the receiver, then frames must be stored until their use, and after consumption of the frame, feedback is compulsory in stop and wait.