Consider the ATM ABR virtual circuit in Figure 6.27, segmented into two control loops at switch S2.
(a) Suppose resource manager cell RM1 departs from S2 to H1 reporting a high available rate, but right afterward an RM cell arrives at S2 from H2 reporting a low available rate for the second half of the circuit. What problem might S2 now face?
(b) When S2 receives RM1 from H1, it might simply hold it while it sends its own RM2 to H2 and back. When RM2 returns, S2 would now send back RM1, reducing its rate specification if necessary. Why might such a strategy be undesirable? Hint: Recall the purpose of segmentation into smaller control loops.
