Problem: Consider an institutional network is connected to the Internet through an access link of capacity 1.544 Mbps. The network services web requests from about 150 users in it. The institution is considering putting up a web cache which can act as a proxy server for all these users. That is, whenever a user makes a web request, the request is first sent to the proxy server to see if it can service the request from its cache. Otherwise, the proxy forwards the requests to the origin server in the public Internet. The users make on the average 1 request per second, with an average size of a requested object being 10 Kbits.
(a) What percentage of the bandwidth of the access link is consumed by the web traffic when there is no proxy server, and all requests are serviced by the origin server?
(b) After installing the proxy server, it was found that the hit rate to the cache is 40%. What percentage of the access link bandwidth is now consumed by the Web traffic?
(c) If the round-trip time (RTT) from a user node to the proxy server is 50ms, and the RTT from the proxy server into the Internet is 2 sec, then what is the average delay experienced by web requests in scenario (b).