Question 5 (8p) P9 on page 175 (Revised). Consider the figure below , for which there is an institutional network connected to the Internet. Suppose that the average object size is 850,000 bits and that the successful probability of network access is 0.1. Also suppose that the amount of time it takes from when the router on the Internet side of the access link forwards an HTTP request until it receives the response is 3 seconds on average.

a) Find the total average response time. (Note: The average access time/delay must be multiplied by the

average number of attempts toward a successful access.)

b) Now suppose a cache is installed in the institutional LAN. Suppose the miss rate is 0.4, which at the same time, increasing the success probability of network access is improved to 0.64. Find the total response time.

Origin servers Public Internet 15 Mbps access link 100 Mbps LAN Institutional network