Microsoft says it will release Windows XP Service Pack 3 by the end of the month, dropping the final shoe needed to complete its NAC architecture, which it calls network access protection (NAP).

The NAP client software is already part of Windows Vista, which is not as widely distributed as XP, so releasing the new service pack will boost the number of NAP-ready endpoints in corporate networks.

The NAP client gathers certain data about the endpoints and passes it up to a verification server that decides whether the data it receives clears the endpoint for admission to the network. In combination with other vendors' client software packages, the NAP client can report much more detail about endpoints than can the NAP client alone.

As a result, in the run up to all the core NAP elements being available to customers, many other vendors have declared their NAP compatibility. These include vendors that sell devices that could be used as enforcement points, such as switches and firewalls, but also sellers of desktop management and security software whose products hold a wealth of information about what endpoints are up to.

The client can work with either Microsoft Server 2008 as the verification server or with third party NAC servers as long as those third parties have worked out compatibility with the NAP client. Hybrid NAC/NAP deployments may be attractive to customers that already have NAC in place but would like to drop the third-party NAC client from their desktops and laptops.

The service pack is scheduled to be added to the Microsoft Download Center April 29, and it will be pushed to customers this summer. It includes other updates and patches.

Tim Greene is senior editor at Network World.