Which metric uses a port number to identify applications?

• A. IP Address
• B. Port Number
• C. MAC Address
• D. Hostname

Answer: (B)

Port numbers are how the transport layer directs data to the correct application on a device. An IP address finds the computer on the network, but multiple services run on that single device. The port number tells TCP or UDP which running program should handle the incoming data, such as 80 for web traffic or 443 for secure web. The MAC address identifies the physical network interface on the local link, and a hostname is a human-friendly name that resolves to an IP address. So the feature that uses a port number to identify applications is the port number itself.