If you first domain controller within a domain was running Windows Server 2008 or later you should be using DFS-R (Distributed File System Replication). If you upgraded from Windows 2003 domain, there is a big chance that you are still using FRS (File Replication Service).

To be sure, run following command on one of your DCs:

dfsrmig /getmigrationstate

If response is “Start” it means you are using FRS
If response is “Eliminated” it means you are using DFS-R

The response indicates the state of FRS to DFS-R migration process. Following states are possible:

0 – “START”
1 – “PREPARED”
2 – “REDIRECTED”
3 – “ELIMINATED”

Windows Server 2008 and later