RemoteApp is an application delivery method of Windows 2008 Remote Services using remote desktop mechanism. It’s in primitive state and there are security concerns, but it is fast and promising. When we setup this service for the first time, some users could not connect to the remoteapp and a pop up error occurred saying “The remote computer requires Network Level Authentication“. This error occurred only in Windows XP SP3 clients.
Network Level Authentication is an authentication method that can be used to enhance RD Session Host server security by requiring that the user be authenticated to the RD Session Host server before a session is created. After some investigation, we found out that to use Network Level Authentication, you must meet the following requirements:
- The client computer must be using at least Remote Desktop Connection 6.0.
- The client computer must be using an operating system, such as Windows 7, Windows Vista, or Windows XP with Service Pack 3, that supports the Credential Security Support Provider (CredSSP) protocol.
- The RD Session Host server must be running Windows Server 2008 R2 or Windows Server 2008.
Since our clients were fully patched, it seemed that CredSSP protocol was not enabled in our XP clients. Looking further on this, we find out a related article from Microsoft at http://support.microsoft.com/kb/951608.
You can download a Microsoft Fix it executable at http://go.microsoft.com/?linkid=9758284 to turn on CredSSP protocol on Windows XP SP3 or try the registry modification mentioned in Microsoft’s article.