2. Consider a web client requesting a html page of size 0 = 125,000 bytes from a web server. This html page contains no objects. The RTT= 300ms, and the channel

rate C = 20Mbps. Assume the client uses non-persistent HTTP (HTTP 1.0). Now, a web cache (proxy server) is installed in a location where the RTT between this web cache server and the web server is 400ms and the channel rate is 20Mbps. The RTT between this web cache server and the client is 50ms and the channel rate is 100Mbps. In answering this question, assume error-free transmission and no local cache in the client. Be sure to consider TCP connection establishment (1 RTT), and the data transmission delay for the html file. Ignore header / control bits, and assume that the sending rate is not limited by flow control. Also, please distinguish web cache from router's store-and-forward mode, i.e., the web cache can start sending responses to the client when the first byte of the response is received from the web server. To support your answer, include a timing diagram, and show all steps of your calculations. a. How long is the response time when web cache contains the response? b. How long is the response time when web cache does not contain the response? [extra pts] What is the minimal cache hit rate to make this web cache installation a performance win on average? c.