CompTIA Security+

Answer: A - 802.1x describes port based network access control

Key Takeaway: PNAC is described by the IEEE 802.1x standard. The concept behind this scheme is that an authenticator using RADIUS will not allow a client, or supplicant, access to the network without being authenticated. This authentication system is similar to going across a national border wherein the security agent will not let you cross until you produce a valid passport.