Question

P7. Suppose within your Web browser you click on a link to obtain a Web page. The IP address for the associated URL is not cached in your local host, so a 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; the successive visits incur an RTT of RTT1, . . . , RTTn. Further suppose that the Web page associated with the link contains exactly one object, consisting of a small amount of HTML text. Let RTT0 denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object?

Answer 1

The time elapses from when the client clicks on the link until the client receives the object is RTT0 + RTT1 + RTT2 + ... + RTTn.

Step-by-step explanation:

The time it takes for a client to receive an object after clicking on a link can be estimated using the round-trip time (RTT) and the number of DNS servers visited.

Let's assume that the client needs to visit n DNS servers before receiving the IP address. Each visit incurs an RTT of RTT1, RTT2, ..., RTTn.

Additionally, there is an initial RTT0 between the client and the server containing the object.

Assuming zero transmission time of the object, the total time elapsed would be the sum of the RTTs and RTT0.

So, the time from when the client clicks on the link until the client receives the object is:

Total Time = RTT0 + RTT1 + RTT2 + ... + RTTn