Networking

to retrieve a We Problen 4 (20 points): Hosts A and B in the same FIT network both want at a URL www.networkutopia.con/index.html. The Web page consists only of th (no other objects). There is a Web cache (proxy server) inside the FIT network as shown in Figure 2 and the hosts' browsers are configured so that all HTTP requests are directed to the Web cache. assume that the HTTP GET request message (or its resulting TCP packet) and other TCPF are all of negligible size, i.e., their transmission HTTP response message with the index html file is 100 kbits long, Ignore all other processing del or queueing delays. We delays are all zero, while the packet containing the . The one-way propagation delay from either host A or B to the Web cache is 10 msec. The one-way propagation delay from any host in the institutional notwork (including the Web cache) to the origin server is 200 maes There is no other hosts or cache or server in the network . Link speed between the router R1 and the origin server is 1 Mbps, while it is 10 Mbes t LAN (link between any host and the Web cache) tain the index html file for the above URL . Initially at tO, the Web cache does not con Note: a TCP connection between an HTTP client and it transport HTTP request and response messages. The TCP s corresponding server is established to connection from a host to its cache open until the same host receives the index html file. The TCP connection establisha should also be taken into account in the following problems. origin server 1 Mbps aneway propagation 1 Mbps delay: 200 msec 20 R1 Web cache 10 Mbps FIT network (LAN) one-way propagation delay: 1o Figure 2: Network for Problem 4 (a) (16 points) Suppose that host A makes an HTTP request at t 0. Calculate the total response time, i.e., the time from when host A requests the URL www.networkutopia.com/index.html to t time when the requested Web page is received and displaced. Do not simply write down the numbers. You should show your steps along with brief explanation for each step. 0.21 sec. o, o 2 +40.1 pr (b) (10 points) After 10 minutes, suppose that host B makes an HTTP request for the same URL Calculate the total response time for host B. Do not simply write down the numbers. You should show your steps along with brief explanation for each step