Hi,
Initially, Active Directory was only in charge of centralized domain management. However, Active Directory became an umbrella title for a broad range of directory-based identity-related services.
A server running Active Directory Domain Service (AD DS) role is called a domain controller. It authenticates and authorizes all users and computers in a Windows domain type network—assigning and enforcing security policies for all computers and installing or updating software.
If you mean have DCs in specific sites, it will help ensure a healthy network, monitor replication regularly; Making the utilization of network bandwidth between sites less efficient.
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Best Regards,