GATE CSE 2024 | Set 1 | Question: 6

Question

A user starts browsing a webpage hosted at a remote server. The browser opens a single TCP connection to fetch the entire webpage from the server. The webpage consists of a top-level index page with multiple embedded image objects. Assume that all caches (e.g., DNS cache, browser cache) are all initially empty. The following packets leave the user's computer in some order.

1. HTTP GET request for the index page
2. DNS request to resolve the web server's name to its IP address
3. HTTP GET request for an image object
4. TCP SYN to open a connection to the web server

Which one of the following is the CORRECT chronological order (earliest in time to latest) of the packets leaving the computer?

• A. $\text{(iv), (ii), (iii), (i)}$
• B. $\text{(ii), (iv), (iii), (i)}$
• C. $\text{(ii), (iv), (i), (iii)}$
• D. $\text{(iv), (ii), (i), (iii)}$

Answer 1

Correct Answer - Option C
The standard sequence of operations when trying to reach a server are as follows. 

1. Device checks with local DNS server to identify the destination IP address. 
2. Since HTTP uses TCP network protocol, it has to setup a link with the webserver, hence it sends a syn packet to the server's IP that was resolved using DNS query. 
3. After a TCP connection has been established, The host would request for an index of the webpage using the HTTP GET command. 
4. Based on the Index recieved, Host would make further requests to get the other information that it made the connection for. 
   
   Option C would be the best fit for the discussed sequence 

Answer 2

The answer to this would be

Option C.