Suppose within your Web browser, you click on a link to obtain a Webpage. The IP

Question

Suppose within your Web browser, you click on a link to obtain a Webpage. The IP address for the associated URL is not cached in your local host. Suppose that n DNS servers should be visited before your host receives the IP address. The successive visits incur an RTT of RTT1, RTT2, ..., RTTn. Suppose that the base HTML file associated with the link references three very small objects (small pictures) on the same server. Let RTT0 denote the RTT between the local host and the server containing the objects. Neglecting transmission times, how much time elapses with Non-persistent HTTP with no parallel TCP connections? Persistent HTTP with no parallel TCP connections? Non-persistent HTTP with parallel connections? Persistent HTTP with pipelining?

Explanation / Answer

Solution:

The total time required to get the IP address = RTT1+ RTT2+ ....... + RTTn

After obtaining the IP address, RTT0 elapses on connection request to TCP/IP and another RTT0 spent on requesting and receiving the small object.

Therefore the total request time will become:

2RTT0+ RTT1+ RTT2 ....... + RTTn

a) For receiving the html file for each of the three objects will be

RTT1+ RTT2+ ....... + RTTn + 2RTT0 + 3* 2RTT0

= 8RTT0 + RTT1+ RTT2+ ....... + RTTn

b) here we need to consider time to request receive 3 referenced object from same connection, so we get

RTT1+ RTT2+ ....... + RTTn + 2RTT0 + 3RTT0

= 5RTT0 + RTT1+ RTT2+ ....... + RTTn

c) The parallel connections take another 2RTT0 will be

RTT1+ RTT2+ ....... + RTTn + 2RTT0 + 2RTT0

= 4RTT0 + RTT1+ RTT2+ ....... + RTTn

d) Now, here we require another RTT0 for three objects, so we get

RTT1+ RTT2+ ....... + RTTn + 2RTT0 + RTT0

= 3RTT0 + RTT1+ RTT2+ ....... + RTTn

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