Which technology enforces port access control so clients cannot connect without authentication remediation?

802.1x is a port-based network access control protocol that requires clients to authenticate before gaining access to the network. It prevents unauthorized devices from connecting by placing them in a restricted VLAN or denying access until successful authentication. 802.11n is a Wi-Fi standard, not an access control mechanism. MAC Authentication Bypass (MAB) is a method for authenticating devices based on their MAC address, often used for devices that cannot perform 802.1x, but it doesn't enforce the same level of port access control as 802.1x. IP Source Guard is a security feature that prevents IP spoofing by filtering traffic based on IP and MAC address bindings, not port access control.