Request.ServerVariables["LOGIN_USER"]:
Request.ServerVariables["AUTH_USER"]:
Request.ServerVariables["REMOTE_USER"]:

HttpContext.Current.User.Identity.Name:
HttpContext.Current.User.Identity.IsAuthenticated: False
HttpContext.Current.User.Identity.AuthenticationType:

System.Security.Principal.WindowsIdentity.GetCurrent().Name: IIS APPPOOL\License Manager