FN_MS_ACL_INFO is a SAP Parameter attribute which is used to control file name for message server acl file information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
ACL file of the message server, which stores details of the hosts from
which application servers can log on.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.