Network Access Control (NAC) refers to methods used to control access by users and devices to corporate networks. Digital certificates can be used as a secure authentication mechanism in this context.
A typical use case is certificate-based authentication using IEEE 802.1X. A device or user authenticates when accessing a LAN or Wi-Fi network, for example. An authentication service such as RADIUS verifies the identity and determines, based on the configured policies, whether network access should be granted.