Graphical simulation of Go-back N protocol & Selective Repeat protocol
Error checking and correction of Frames.
The Go Back N ARQ is an Automatic repeat request protocol that allows multiple frames to be transmitted without an acknowledgement (ACK). Note that Ws=Window size.
Frame 0 to frame 7(Ws-1) are all transmitted without acknowledgement. If ACK is received for frame 0 before window is exhausted transmitter continues to transmit.
Also if the ACK for frame 0 is lost or damaged thus not received, transmitter goes back to N of the window and starts to retransmit.
No need to wait for acknowledgement before sending another frame.
There is need to transmit all frames subsequent to lost frame or error frames
The Selective repeat ARQ has an increased windows size that gives allowance for out of order and error frames to be accepted .
The receiver can send a negative acknowledgement (NACK) corresponding to the frame not received in a sequence of frames.
This is in addition to ACK commands that is normally received when frames are sent from the sender.
Receiver window maintains a buffer to receive out of sequence frame that can be accepted.
There is need to buffer out of order frames which occupies memory space.
