DC synchronizing problem with AD Utility

[Chris_lyme]

I have 2 DC in my environment DC1 and DC2 which are synchronized and when any change is done in DC1 it takes time to update in DC2
I have tried third party utility vendor and add DC2 in that software but problem still there it taking many hours to update in DC2 while change done in DC1

both DC are not in same location and I am using windows server 2008

what could be the problem, any help would be appreciated !

 

[aford10]

Is there anything on the network inbetween them, such as a firewall?

 

[Chris_lyme]

There must be a firewall inside the network actually the problem is arisen in the environment in on of our client, I do not clarify this with him as i want some homework about the issue so just wanted that what could be the issue behind this problem that we should need to monitor