DS has a feature to be a consumer for a legacy supplier (4.x). This feature was no longer needed and has been removed from the code. Thus it could be dropped from the documentation as well. See BZ#1208694. https://access.redhat.com/documentation/en-US/Red_Hat_Directory_Server/10.1/html/Administration_Guide/Managing_Replication-Replication_with_Earlier_Releases.html
I removed the following sections about legacy replication from our guides (10.0, 10.1, and master branch): Admin Guide: 11.1.8. Replication with 4.x Versions of Directory Server 11.19. Replication with Earlier Releases + one glossary entry Configuration, Command, and File Reference: 3.4.2. Legacy Replication Attributes 4.1.31. Legacy Replication Plug-in 6.4. copiedFrom 6.5. copyingFrom 4.1.31. Legacy Replication Plug-in + one glossary entry Plug-in guide: One glossary entry
*** This bug has been marked as a duplicate of bug 1208696 ***