Problem 2.16

     In part (b), assume that no frames are lost.

     Additional hint:  When the receiver gets a frame, it can do only a finite number of things (e.g., return an ack, release frame to
     higher protocol layer, etc.)  Construct two scenarios represented by two diagrams (like Fig. 2.19) that the receiver cannot
     distinguish.  So whatever rule the receiver uses when it receives a frame, in one scenario the receiver will malfunction.
     Problem 2.18

     When Bertsekas and Gallager say "but focusing on the packets from B to A" they mean "illustrate the flow of packets from B to
     A".

     Make a xerox copy of Figs. 2.25 and 2.26. White-out the SN's and RN's in the boxes. White out the arrows and numbers
     showing packet releases. White out the lines and numbers showing window sizes. Then write the solution on the xerox copies.

     Assume that, on a timeout, the sender transmits the entire window in increasing SN order.
     Problem 2.19

     Consider simultaneous, 2-way traffic.

     Modify rule 4 on page 75 to say, "If an error-free frame is received that will be released to the higher layer in Step 2 of node B
     on page 76 then..."

     Hint: Don't forget that Node A has four variables to examine: variables SNmin, RN as well as the values sent by B of SN and
     RN. Do not confuse RN in step 4 on page 75 (the variable) with RN in step 2 on page 76 (the value in a message).