1. Compare the operation of Stop-and-Wait ARQ with bidirectional Go-Back-N ARQ with a window size of 1. Sketch out a sequence of frame exchanges using each of these protocols and observe how the protocols react to the loss of an information frame and to the loss of an acknowledgment frame.

2. Consider a bidirectional link that uses Selective Repeat ARQ with a window size of N = 4. Suppose that all frames are one unit long and use a time-out value of 2. Assume that the one-way propagation delay is 0.5-time unit, the processing times are negligible, and the ACK timer is one-unit long. Assuming station A and B begin with their sequence numbers set to zero, show the pattern of transmissions and associated state transitions for the following sequences of events

a. Station A sends six frames in a row, starting at t = 0. All frames are received correctly.

b. Station A sends six frame in a row, starting at t = 0. All frames are received correctly, except frame 3 is lost.

c. Station A sends six frames in a row, starting at t = 0. Station B sends six frames in a row starting at t =0.25. All frames are received correctly.