(a) Briefly differentiate between HTTP persistent and non-persistent connections

Question

(a) Briefly differentiate between HTTP persistent and non-persistent connections RTT2 Web Server RTT1 RTTHTTP RTTo Local DNS cache Client b) 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 three DNS servers are visited before your host receives the IP address from DNS: The first DNS server visited is the local DNS cache, with an RTT delay of RTTo-1 msecs . The second and third DNS servers contacted have an RTTs of 6 and 10 msecs, respectively.

Explanation / Answer

Ans-a)-HTTP (Hyper Text Transfer Protocol) is a stateless protocol, it doesnot remember the infromation of past client. HTTP connections are of two types.

1)Non-Persistent

2)Persistent

before discussion of persistent and non-persistent discussion we should discuss RTT

RTT(Round Trip Time): time taken to travel a packet from client to server and return back to server.

Non-Persistent:Requires 2 RTT per object

Persistent: Use 1 RTT for all referenced objects

total file transmission time=2RTT+transmit time.

Ans-b)

1-RTT for DNS=1+6+10=17

RTT between local host and web server=2RTT(given)=2*83=166

so total=166+17=183miliseconds.

2-Total time=3*(2*83)+17=3*166+17=515miliseconds.

3-Total time=5*83+17=432

4-otal time=5*83+17=432

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