DFS 2012 the namespace server cannot be added access is denied new namespace wizard

I want to deploy a DFSR with 2 windows server 2012 in AD 2000. When I want to create the first namespace in DFS server, it end up with error "\\domain.com\share. the namespace server \\server\share cannot be added. Access is denied". the domain user I used is a normal domain user without special permissions. So I try to assign full control to the two DFS server in Dfs-configuration OU and System OU. But it didn't work. What permission is needed for the DFS server to create a namespace?