It is desired to send frames of fixed duration T seconds continuously from A to B. A 3-bit send sequence number is included in the frames from A to B. The acknowledgment signal has duration T/4, and is returned by B immediately following each complete receipt of a frame. The go-back protocol is used, and A’s window of allowed transmitted frames is restricted to prevent ambiguity.
a) What is the longest permissible propagation delay in each direction such that continuous transmission is possible under these conditions? Assume propagation delay is the same in both directions and decoding time is negligible. Draw a clear time diagram of the communication events.
b) Suppose one frame is received in error and B immediately after receiving the frame send a REJ signal, same T/4 duration, instead of an acknowledgment. Assuming the go-back protocol, how many frames would have to be re-sent if this is the only frame received in error?
c) Repeat the question of b) if the propagation time is reduced to one-half of the value found in part a)