Check an access node's contention ratio: sold capacity versus uplink, busy-hour demand and the throughput each subscriber really gets.
Oversubscription is normal and necessary: subscribers are neither all online nor all saturating their line at once. The contention ratio describes the worst case, while multiplying by concurrency and average active utilisation gives the load the uplink actually has to carry. A 50:1 ratio can be perfectly good service or a nightly disaster depending on concurrency, so the busy-hour figure — not the ratio alone — is what should trigger an uplink upgrade.
ISP Bandwidth Oversubscription
contention ratio = Σ sold speeds ÷ uplink capacity; busy-hour load = Σ sold × concurrency × average active utilisation.
contention ratio = Σ sold speeds ÷ uplink capacity; busy-hour load = Σ sold × concurrency × average active utilisation. Oversubscription is normal and necessary: subscribers are neither all online nor all saturating their line at once. The contention ratio describes the worst case, while multiplying by concurrency and average active utilisation gives the load the uplink actually has to carry.
A 50:1 ratio can be perfectly good service or a nightly disaster depending on concurrency, so the busy-hour figure — not the ratio alone — is what should trigger an uplink upgrade.
This calculator takes 5 inputs: Subscribers on the access node, Speed sold per subscriber, Uplink capacity, Subscribers active in the busy hour, Average utilisation of an active subscriber. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.