Problem: In this problem, we would like to compare the use of the Go-Back-N and Selective-Repeat error control protocols on a link-by-link basis, on an end-to-end basis.
Consider a network with D hops between the two communicating end devices. The propagation delays of all hops are exactly the same and are equal to L, and the frame/packet transmission time are also equal and are given by T. The packet length in bits is N and the bit error probability is p. Consider only the case in which window is sufficiently large such that the transmitters do not have to wait. Assume that the reverse channel is error free, i.e., the acknowledgments are never corrupted.
Derive expressions for the efficiencies of the above systems, taking all four possible cases into account. Then, identify the maximum achievable efficiency in each of the two strategies, end-to-end and link-by-link under noisy channel conditions.
Using simple probabilistic arguments, and assuming that the delay of a packet is measured from the instant it is transmitted for the first time, find the average end-to-end delay under both strategies, and under both protocols, i.e., four different expressions.
Based on the above, can you make a recommendation for which strategy and which protocol to use?