Question

Assume the average request rate is 4 requests per second, the average object size is 35 Mbits, the average data rate to clients on the LAN is 1 Gbps, the access link rate is 150 Mbps, the RTT to the origin servers is 3 seconds, and there is a web cache on the LAN with a hit rate of 0.45.

What is the average response time?

Answer 1

Solution) The time to transmit an object of size L over a link or rate R is L/R.
The average time is the average size of the object divided byR:
∆ = (36700160 bits) / (1000000000 bits/sec) = 0.0367 sec.

Note: 35 Mbits= 36700160 bits and 1 Gbps= 1000000000 bits

The traffic intensity on the link is given by

β∆ = (4requests/sec) / (0.0367sec/request) = 0.146.

Thus, the average access delay is (0.0367 sec) / (1 −0.146)=0.0042 seconds.

The total average response time is therefore 0.0042 sec+ 3sec = 3.0042 sec or 3 seconds