Active Directory Replication Tuning

Hi!

I have MS Windows 2003 R2 domain controllers a
I need to tune replication level in active directory but this parameter not affect 🙁

replication compression level = 9

(HKLM\CCS\Services\NTDS\Parameters / REG_DWORD: Replicator compression level)

Who use this parameter ? What`s wrong ?
Or how i can tune replication on slow wan link ?
*MS articles i saw