What is Network Access Quarantine Control in Windows Server 2003

The Network Access Quarantine Control in Windows prohibits network access to a private network unless the machine connecting to the network is validated against certain preset conditions. These conditions are checked by an administrator approved script, this is typically enforced by Internet Authentication Service (IAS) and / or Remote Access Servers (RAS)

Network Access Quarantine Control only provides added protection for remote access connections and is not the same as Network Access Protection, which takes the Quarantine Control a step further and enforces it on remote RAS and VPN connections and DHCP allocation. You can read more about the Network Access Protection (MS-NAP) in an article we published here
Typically you would need IAS server and use the Network Connection Manager kit to configure remote quarantine connections
An excellent resource on deploying the Network Access Quarantine Control (NAQC) can be found at http://www.securityfocus.com/infocus/1794 .