Windows 2003 – Site Topology-Site Links

Hi Experts

I am currently designing a 2003 replication topology for a large single domain network, the network consists of a central hub site which has three AD domain controllers and 80+ slow wan sites – each wan site has a domain controller.

My question is relating to the site link on one particular site – he is my layout

3 DC’s at CENTRAL SITE
1 DC at SITE A
1 DC at SITE B

SITE A has a physical connection to SITE B
SITE A has a physical connection to CENTRAL SITE
SITE B has a physical connection to CENTRAL SITE

I would prefer SITE A to replicate directly to CENTRAL SITE, and only chain through to SITE B if the link to CENTRALSITE becomes unavailable – Do I need to tell AD about this ?

I hope I have explained well enough, thanks for your help in advance.