Consider selective repeat, where the maximum window to prevent ambiguity is 2b-1, where b is the number of bits in the sequence number. Suppose b = 5.
Make the assumptions that frames arrive in the order transmitted, if they arrive at all, and that there are no undetected errors in decoded frames.
The current state of the receiver is that it has correctly received all frames up to one numbered 14, is missing frame number 15, has correctly received frame number 16, and is missing all frames newer than the number 16 frame. Note that the sender does not know the exact state of the receiver, but the sender must obey the window constraint.
Given this receiver state, answer the following and explain the reason for your answer:
a) What is the newest frame number the sender could possibly be allowed to send?
b) What is the oldest frame number the sender might still be allowed to send?