The pre-15.1 version of the Request Function Replication topic has been removed from the Replication Server 15.7 Administration Guide Volume 2, as Replication Server versions earlier than 15.1 are no longer supported.
If you have versions of Replication Server earlier than 15.1 in your replication environment, see Replication Server 15.6 Administration Guide: Volume 2 > Appendix C: Pre-15.1 Request Function Replication to replicate request functions in Replication Server.