NTLM is the Windows NT® challenge/response authentication system that was developed for Microsoft Windows NT-based networks. The user’s domain credentials are used to authenticate the client. The Windows domain controller challenges the client to perform a complex mathematical calculation on the user’s domain password and sends this encrypted password to the domain controller. The domain controller then uses the same calculation to decrypt the password. If the decoded password matches the password obtained from the Security Account Manager (SAM) database, then the client is authenticated. The client is then allowed to log onto the network and access network resources. The RTC application may choose to specify RTCAU_NTLM in the <Allowed Auth> tag to indicate that this is an authentication scheme that the client will accept when challenged by the server.