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: HTTP GET request for the index page DNS request to resolve the web server’s name to its IP address HTTP GET request for an image object 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. (iv), (ii), (iii), (i)
• B. (ii), (iv), (iii), (i)
• C. (ii), (iv), (i), (iii)
• D. (iv), (ii), (i), (iii)

Hint:

The sequence of operations while accessing a webpage without cached data involves DNS resolution, connection establishment, fetching the main content, and then retrieving embedded objects.

Answer 1

The Correct Option is C

Step 1: DNS request (ii): The client first sends a DNS request to resolve the server’s hostname to its IP address, as no cache is available. Step 2: TCP SYN (iv): After the DNS response, a TCP SYN packet is sent to establish a connection with the server. Step 3: HTTP GET request for the index page (i): Once the connection is established, an HTTP GET request for the index page is sent. Step 4: HTTP GET request for image objects (iii): After receiving the index page, HTTP GET requests for the embedded image objects are sent. Final Answer: \[ \boxed{(ii), (iv), (i), (iii)} \]