802.1X provides port-based authentication, which involves communications between a supplicant, authenticator, and authentication server. Port refers to a single point of attachment to the LAN infrastructure. The supplicant is often software on a client device, such as a laptop; the authenticator is a network device, such as an ethernet switch or wireless access point; and the authentication server is typically a host running software capable of speaking the RADIUS and EAP protocols.
You can implement 802.1x solution without NAC by using open standards radius servers.
Where NAC is solution which enforces your organization’s network security policies on all devices seeking network access. Cisco Network Admission Control (NAC) allows only compliant and trusted endpoint devices, such as PCs, servers, and PDAs, onto the network, restricting the access of noncompliant devices, and thereby limiting the potential damage from emerging security threats and risks. Cisco NAC gives organizations a powerful, roles-based method of preventing unauthorized access and improving network resiliency.
We are usign 802.1x authentication for all our wireless users by using microsft radius server comes with Windows 2003 server.