Compare scrubbing capacity against a modelled attack volume to see whether your DDoS headroom ratio actually holds.
Volumetric defence is a simple ratio problem: divide the scrubbing capacity you can actually invoke by the attack volume you plan against. A ratio below 1 means the attack saturates the scrubber; below 1.5 means you have no margin for the attack growing mid-event, which is exactly what attackers do when the first wave fails. Any attack larger than your internet link saturates it before a single on-premises appliance sees a packet, which is why the survival ratio, not the appliance datasheet, decides whether you stay online.
DDoS Capacity
headroom ratio = scrubbing capacity ÷ attack volume; on-premises survival ratio = link capacity ÷ attack volume.
headroom ratio = scrubbing capacity ÷ attack volume; on-premises survival ratio = link capacity ÷ attack volume. Volumetric defence is a simple ratio problem: divide the scrubbing capacity you can actually invoke by the attack volume you plan against. A ratio below 1 means the attack saturates the scrubber; below 1.5 means you have no margin for the attack growing mid-event, which is exactly what attackers do when the first wave fails.
Any attack larger than your internet link saturates it before a single on-premises appliance sees a packet, which is why the survival ratio, not the appliance datasheet, decides whether you stay online.
This calculator takes 4 inputs: Scrubbing capacity available, Modelled attack volume, On-premises internet link capacity, Normal legitimate traffic. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
Scrubbing capacity is shared across every customer of the provider, attacks routinely double when the first attempt is mitigated, and reflection vectors can add hundreds of gigabits in seconds. A 3× ratio absorbs a simultaneous second target and an attack that escalates without renegotiating capacity mid-incident.