Domain Controller Requirements
If you are trying to place a DC in a site, here are some of the requirements to help you decide if your network needs to add an extra Domain Controller.
1.The minimum amount of users should be more than 100 users in a site.
2.A site is connected to other sites via a WAN link slower than 256Kbps
3.WAN bandwidth utilization during peak times exceeds 90 percents.
4.The WAN connectivity to other sites is not always available.
5.Users in a site use an application that often queries the Domain Controller (Global Catalog)