IPA is an identity solution stack, of which the following is included:

  LDAP
  Kerberos
  NTP
  DNS

Red Hat Directory Server is just a LDAP implementation - which, incidentally, is based on Fedora 389 Directory Server, which, in turn, is included in IPA.

https://docs.fedoraproject.org/en-US/Fedora/18/html/FreeIPA_Guide/Configuring_an_IPA_Client_on_AIX.html

https://www.freeipa.org/page/SUDO_Integration_for_AIX

https://www.server-world.info/en/note?os=CentOS_7&p=ipa