Identify the correct sequence in which the following packets are transmitted…
20162025
Identify the correct sequence in which the following packets are transmitted on the network by a host when a browser requests a webpage from a remote server, assuming that the host has just been restarted.
- A.
HTTP GET request, DNS query, TCP SYN
- B.
DNS query, HTTP GET request, TCP SYN
- C.
DNS query, TCP SYN, HTTP GET request
- D.
TCP SYN, DNS query, HTTP GET request
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Correct answer: C
Answer: DNS query, TCP SYN, HTTP GET request.
Step 1: DNS query to resolve the website's hostname to an IP address. After a restart the host typically has no DNS cache, so this must be done first.
Step 2: TCP three-way handshake begins (TCP SYN is sent). A TCP connection must be established before sending HTTP data.
Step 3: Send the HTTP GET request over the established TCP connection.
Note: If the host already knew the IP (for example from a cache), the TCP SYN could come before a DNS query. The question specifies the host was just restarted, so DNS first is the expected behavior.
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