Size a data centre interconnect from daily change rate, replication window, RPO and distance latency.
Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km. DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
DCI Bandwidth
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01.
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01. Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km.
DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
This calculator takes 6 inputs: Daily data change, Replication window, Recovery point objective, Reduction from compression and dedup, Peak-to-average factor, Distance between sites. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.