tutorial-3_semA2023_student

Tutorial 3, CS5222, Sem A, 2023-24 Problem 3. Suppose within your browser you type in a URL to obtain a webpage. The IP address for the associated URL is not cached in your local host, so as DNS lookup is necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS; Visiting the i -th of the them incurs an RTT i per DNS. Further suppose the HTML file references eight very small objects on the same server. Let RTT 0 denote the RTT between the local host and the server containing an object. Neglecting transmission times, how much time elapses with a. Non-persistent HTTP with no parallel TCP connections? A) RTT 1 + … + RTT n + 8RTT 0 B) RTT 1 + … + RTT n + 9RTT 0 C) RTT 1 + … + RTT n + 16RTT 0 D) RTT 1 + … + RTT n + 18RTT 0 b. Non-persistent HTTP with the browser configured for 5 parallel connections? A) RTT 1 + … + RTT n + 4RTT 0 B) RTT 1 + … + RTT n + 5RTT 0 C) RTT 1 + … + RTT n + 6RTT 0 D) RTT 1 + … + RTT n + 7RTT 0 c. Persistent HTTP? A) RTT 1 + … + RTT n + 8RTT 0 B) RTT 1 + … + RTT n + 10RTT 0 C) RTT 1 + … + RTT n + 12RTT 0 D) RTT 1 + … + RTT n + 14RTT 0 Problem 4. (Looking up an IP address using nslookup) You can type nslookup followed by the hostname you want to look up (e.g., type “nslookup ebay.com” in the command prompt), and nslookup will issues a DNS query to find out the IP address. a. What is the IP address of the hostname? b. Can you type the IP address in your browser’s address bar and get to the webpage?