Which among the following is DUC(Dynamic Update Client)?

no-ip.com is a well-known Dynamic DNS Update Client (DUC) service. It provides free and paid dynamic DNS services that allow users with dynamic IP addresses to have a static hostname that automatically updates when their IP changes. While other services like dyn.com also exist, no-ip.com is specifically recognized as a DUC provider in the context of RAT and malware callbacks for maintaining stable connections to dynamic-IP systems.