2. (7 marks) [DNS, Web application (Learning Outcomes 2, 3)] Suppose in the address bar of your web browser you enter a URL to obtain a Web page, which contains the hostname of the Web server hosting the Web page. The IP address of the Web server is not cached in your local host, so a DNS lookup is necessary to obtain the IP address. Suppose n DNS servers are visited before your host receives the IP address; the successive visits incur an RTT of RTT1, ..., RTTn, respectively. The web page at the URL contains one HTML file of size a, which references 3 images on the same Web server, of size b, c and d, respectively. Let RTTo denote the RTT between your local host and the Web server. Ignore any detailed nodal processing, queueing or transmission delay at your local host, DNS servers and the Web server, but only consider the respective RTT. (1) How much time elapses from when the client enters the URL in the Web browser until the client receives the IP address of the Web server? (2) Consider the three-way handshake procedure between your web browser and the Web server for retrieving Web objects. Suppose the client Ack in the third step of three-way handshake is piggybacked onto the TCP segment carrying the first HTTP request. If persistent connection is used (as in HTTP 1.1), how long does it take from when your web browser initiates the three-way handshake procedure to when your browser has received all Web objects to display the complete Web page