Authenticator strength is enforced using slapo-ppolicy overlay for LDAP. The ppolicy overlay is then configured to use PAM cracklib to enforce complexity.
For the default password complexity rules see the faq-password-complexity FAQ.
The integration point between the remote LDAP server and PAM is the pam_ldap pam module. SIMP configures pam_ldap to point to the SIMP LDAP server and communicates using TLS.
References: IA-5 (1)(a), IA-5 (1)(e)