A new SDK and associated download will help Windows developers build peer-to-peer (P2P) applications. P2P applications such as Groove Networks, as well as popular file- and music-sharing software like Kazaa, allow users to find each other, communicate, and share files directly without the aid of Internet servers. The Windows XP Peer-to-Peer SDK and Peer-to-Peer Update, available now in beta form, provide some of the core functionality required by P2P applications. Microsoft believes that these applications could provide an incentive for users to upgrade to Windows XP, but only if certain technical issues are resolved.

The SDK includes a set of extensions to Windows XP, along with a set of Win32-based developer APIs (as opposed to the newer style of APIs included in the .NET Framework) and documentation. Applications built with the SDK will require an additional component, the Windows XP Peer-to-Peer Update, which includes an updated Internet Protocol version 6 (IPv6) stack as well as an IPv6 firewall to protect end-users’ machines from unwanted IPv6 traffic. Microsoft is also distributing this component with its own P2P applications, starting with threedegrees, a client for younger consumers that includes instant messaging and digital-media-sharing functions. (See "NetGen Team Targets Youth".)

Applications built with the SDK can use the following features:

Name resolution allows applications to resolve client names to an IPv6 endpoint (a combination of IPv6 address and port number), which is important in environments where a Domain Name System (DNS) infrastructure may not be available, such as home networks.

Network grouping adds the ability for multiple applications to share the same set of data, as well as the ability to make sure that only invited peers can participate.

Identity manager allows applications to create, enumerate, and manage the identities by which the user participates in P2P applications.

Technical documentation and information on how to obtain the Windows XP Peer-to-Peer SDK and Update is available at msdn.microsoft.com/downloads/list/winxppeer.asp.