Windows Authentication for Informix Mapped Users

This is the Part 2 to my earlier question on how to permit Win Active Directory authenticated user to access Informix. I have initial guidance from Fernando Nunes to use the 'Mapped Users' feature available on Informix v11.70.FC7. I also have a high level understanding now of how the /etc/pam.conf and /etc/pam_user.conf collaborate to authenticate a user access on the server (HP-UX 11.31 ia64). I am also familiar with use of USERMAPPING Informix config. parameter and 'surrogate users and roles' with 'Mapped Users'. What I do not know anything about is how does AD authenticated login link/connect/recognize the Informix server. Is there an add-on to AD that does this? Guidance on this would be helpful for me to start putting the pieces together.