First let me give you the specfications of the two servers involved. Server 1: Windows Server 2003 Apache 2.2 32bit PHP 5.2.10. Server 2: Windows Server 2012 R2 Standard Apache 2.4 64bit PHP 5.6.5. To read the Windows remote user (for a Single Sign-on) I use the module mod_auth_sspi on the older server. Unfortunately this module isn't supported. SSSD stands for System Security Services Daemon. SSSD talks to remote directory services that provide user data and provides various authentication methods, such as LDAP, Kerberos, or Active Directory (AD). It also provides an NSS (Name Service Switch) and PAM (Pluggable Authentication Module) interface.