Explain Simplest Protocol and Stop and Wait Protocol for Noiseless Channel.

Question: Explain Simplest Protocol and Stop and Wait Protocol for Noiseless Channel. 

Answer 

Noiseless Channel

An ideal channel in which no frames are lost, duplicated or corrupted is regarded as Noiseless Channel.

Simplest Protocol

• In simplest protocol, there is no flow control and error control mechanism. It is a unidirectional protocol in which data frames travel in only one direction (from sender to receiver).
• Also, the receiver can immediately handle any received frame with a processing time that is small enough to be negligible.
• The protocol consists of two distinct procedures :a sender and receiver. The  sender runs in the data link layer of the source machine and the receiver runs in the data link layer of the destination machine. No sequence number or acknowledgements are used here.

Stop and Wait Protocol

• The simplest retransmission protocol is stop-and-wait.
• Transmitter (Station A) sends a frame over the communication line and then waits for a positive or negative acknowledgement from the receiver (station B).
• If no error occurs in the transmission, station B sends a positive acknowledgement (ACK) to station A.
• Now, the transmitter starts to send the next frame. If frame is received at station B with errors, then a negative acknowledgement(NAK) is sent to station A. In this case, station 'A' must retransmit the old packet in a new frame.
• There is also a possibility that the information frames or ACKs may get lost.
• Then, the sender is equipped with a timer. If no recognizable acknowledgement is received when the timer expires at the end of time out interval,  the same frame is sent again.
• The sender which sends one frame and then waits for an acknowledgement before the process is known as stop and wait.