58. 性能分析
1. For one or more selected protocols, make a study of protocol performance,
measured in payloads delivered per second, as a function of the checksum
error rate, lost packet rate, and timeout interval. For example, provide
graphs showing payloads/sec as a function of timeout interval, for
various error rates. What can you conclude?
Efficienciy = F ( timeout _interval , loss_rate , err_rate )
Throw a sprat to catch a whale.
65. 性能分析
Q:Compare the performance of protocols 5 and 6 in detail with respect to
payloads/sec and number of retransmissions for a wide variety of
parameters. Under which circumstances is protocol 5 better? protocol 6?
Q: The function pick_event() has built-in priorities for events. For example,
for protocol 5, frame arrivals go before timeouts. Experiment with
changing these priorities (by reordering the statements in pick_event().
What conclusions can you draw?
Q: Investigate the number of retransmitted frames as a function of the
timeout interval for various parameters? Can you determine what the
optimum setting should be?
Q:Presently, the simulator advances time one tick at a time. If both
processes are blocked on distant timeouts, this process goes slowly.
Change the simulator to advance time more quickly when both processes
are blocked on the clock.
Q:In the simulator at present, packet delivery is essentially instanteous.
Change it so that delivery times are variable with a user-settable
variance. How does the variance affect protocol performance?
…… ……
——One solved questions lead to more……