Which port number is associated with the Domain Name System (DNS) protocol?

The Domain Name System (DNS) protocol operates using port number 53. This port is essential for both DNS query and zone transfer activities, enabling the resolution of human-readable domain names (like www.example.com) into IP addresses that computers use to identify each other on the network.

Understanding port numbers is crucial in networking, as different services run on different ports. Port 53 is well-documented and standardized, making it a reliable reference for DNS configurations in firewalls and routers. Ports like 68, 22, and 389 are associated with other services: port 68 is primarily used for DHCP client requests, port 22 is used for SSH (Secure Shell), and port 389 is associated with LDAP (Lightweight Directory Access Protocol). Thus, recognizing port 53 as the correct answer reinforces not only the role of DNS in network infrastructure but also the significance of knowing various protocol ports in managing and troubleshooting networked environments.