Active Directory Replication Calculator
Estimate AD replication traffic per cycle, site link utilisation and end-to-end convergence time.
Inputs
Worst-Case Convergence Time
90min
Replication Bytes Per Cycle
488 KiB
Transfer Time Per Cycle
0.40s
Site Link Utilisation
0.044%
Changes Per Cycle
1,250
Step by step
Values used
Domain controllers = 12 DCs; Directory changes per hour = 5,000 changes/h; Bytes per changed object = 2,400 bytes; Replication interval = 15 min; Site link bandwidth = 10 Mbit/s; Inter-site compression ratio = 6 ×
Active Directory Replication
bytes per cycle = changes per hour × interval ÷ 60 × bytes per object ÷ compression ratio.
Ring topology convergence
convergence = ceil(DCs ÷ 2) × replication interval
Worst-Case Convergence Time
= 90 min
Replication Bytes Per Cycle
= 500,000
Transfer Time Per Cycle
= 0.40 s
Site Link Utilisation
= 0.044
Changes Per Cycle
= 1,250
How it works
The KCC builds a bidirectional ring within a site, so a change travels at most half the ring to reach every controller, one replication interval per hop. Traffic per cycle is the change volume in the window, compressed for inter-site links. Convergence time, not bandwidth, is usually the constraint: with a 15-minute interval and twelve controllers a password change can take an hour and a half to be visible everywhere.
Formulas
Active Directory Replication
bytes per cycle = changes per hour × interval ÷ 60 × bytes per object ÷ compression ratio.
- changes per hour
- Object modifications originating anywhere in the domain
- bytes per object
- Replicated attribute payload plus metadata
- compression ratio
- AD compresses inter-site replication roughly 6–8×
Ring topology convergence
convergence = ceil(DCs ÷ 2) × replication interval
- DCs
- Domain controllers in the replication ring
- ceil(DCs ÷ 2)
- Worst-case hop count around a bidirectional ring
Frequently Asked Questions
How is Active Directory Replication calculated?
bytes per cycle = changes per hour × interval ÷ 60 × bytes per object ÷ compression ratio. The KCC builds a bidirectional ring within a site, so a change travels at most half the ring to reach every controller, one replication interval per hop. Traffic per cycle is the change volume in the window, compressed for inter-site links.
Why does Active Directory Replication matter?
Convergence time, not bandwidth, is usually the constraint: with a 15-minute interval and twelve controllers a password change can take an hour and a half to be visible everywhere.
What values do I need to enter?
This calculator takes 6 inputs: Domain controllers, Directory changes per hour, Bytes per changed object, Replication interval, Site link bandwidth, Inter-site compression ratio. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
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