P1(10pts). In class we discussed the ABP protocol as described in Figure 3.13 in the book. The "desired" behavior of this protocol is shown in Figure 3.14a. (The book on page 207 2nd parahraph 3rd line calls it "normal operation" and that is not a correct statement.) I changed the code sequences to demonstrate how the confusion may arise when writing protocols. However, without any changes in the code of Figure 3.13, the algorithm will depict the behavior as shown in figure 3.14b.
(a) Verify the behavior by walking through the code. Do you see any problem?
(b) Notice that the desired bahavior as shown in Figure 3.14a is embedded into the depicted behavior in Figure 3.14b. However Figure 3.14b has several extra transmissions, all caused because of the first transmission from node B, namely "B sends (0, 1, B0)". What changes should be made in the code to remove these extra transition?
(c) What happens if you make the changes suggested in part (b) and node A has nothing to transmit to node B but node B has a lot of data to transmit to node A?
P2(5+5pts). The objective of this problem is to familiarize yourself with the network simulator we will be using for next few homeworks. We will study the behavior of stop and wait (given in file p2.c) and PAR (or ARQ given in file p3.c) protocols. Both the protocols do not perform correctly under certain scenarios as discussed in the class. Run the simulator with your choice of parameters and submit a short simulator output which demonstrates that the procols fail. The code for the simulator can be down loaded in your directory from the course web page.