The Backup Domain Controller 

The backup domain controller is a Microsoft Windows domain controller that contains a read-only copy of the master domain directory database that is located on the PDC (primary domain controller). The placement of BDCs Is present in wide-area networks that are based on Windows.

The Backup domain controller belongs to the master domain at each branch office, also called the resource domain. Every Windows NT network needs at least one BDC for fault tolerance. The BDC can be promoted, especially when the PDC fails.

When one or more BDCs belonging to the master domain are used, it will facilitate user logins at branch offices. Subsequently, they can log on to one of these BDCs locally instead of validating it. Through the relatively slow van link by the domain controller at headquarters.

A Windows domain will have zero or more backup domain controllers to load redundancy and load balancing. It will periodically undergo directory synchronization in the Windows domain by repossessing a copy of the directory database from the PDC. It will also perform authentication and validation like PDC but does not manage any accounts.

When you want to make synchronization more efficient. Files can be scheduled with the help of the command to configure different replication rates at additional times of the day. To make it efficient over the WAN link. It would be best to use registry parameters such as changing logo size, or more can be adjusted.

These backup domain controllers are distributed across different geographic locations. With the help of multiple domain controllers, you can provide domain fault tolerance. One of its advantages is that if all the BDCs fail. It will quickly develop a new one on the same site and remove the old ones.