You want to use Perfmon to monitor the performance of Active Directory.
Open the Performance Monitor.
Click on System Monitor in the left pane.
Type Ctrl + I. This will bring up the page to add counters.
Under Select counters from computer, enter the name of the domain controller you want to target.
Select the NTDS performance object.
Select the counters you want to monitor.
After you done with your selections, click Close.
There are several Perfmon counters that can be very valuable for monitoring and troubleshooting Active Directory. The NTDS performance object has counters for address book lookups, inbound and outbound replication, LDAP reads, writes and searches, Kerberos authentication, and the Security Account Manager (SAM).
Here is a list of some of the most useful NTDS counters. I’ve also included their Perfmon explanation, which you can view by clicking on the Explain button in the Add Counters dialog box.
Shows the total number of bytes replicated in. It is the sum of the number of uncompressed bytes (never compressed) and the number of compressed bytes (after compression).
Shows the number of objects received from neighbors through inbound replication. A neighbor is a domain controller from which the local domain controller replicates locally.
Shows the total number of object property values received from inbound ...