A client packet is received by a server with a destination port number of 110. What service is the client requesting?

The correct answer is that the client is requesting the POP3 service.

The destination port number is key to identifying which service is being used. In this case, port 110 is specifically designated for POP3, which stands for Post Office Protocol version 3. This protocol is commonly used for retrieving emails from a mail server. When a client connects to a server and presents a packet with a destination port of 110, it indicates that the client is seeking to download or retrieve emails from the server via the POP3 service.

This understanding of port numbers is essential in networking, as different services and applications utilize specific ports to facilitate communication. Knowing which port corresponds to which service allows network professionals to troubleshoot issues, configure firewalls, and ensure proper service delivery.