Account Bandwidth Calculation

Learn how Incapsula calculates your bandwidth for billing.


Incapsula uses a burstable billing model for calculation of account traffic. This model is based on calculating the 95th percentile of bandwidth usage for billing clean traffic. This enables peaks in usage that exceed the limits of your subscription for brief periods of time. This model is quite common with transit providers and with some CDNs, although many CDNs use an alternative cumulative model, described later in this topic.

How does Incapsula calculate the 95th percentile?

Billing for the entire account's monthly traffic is based on the 95th percentile of bandwidth usage, which is calculated as follows:

  • Incapsula uses 5 minute buckets for calculating the 95th percentile.

  • Each bucket collects all the traffic that passes through the Incapsula network during those 5 minutes:

    • Both incoming traffic (client requests sent to Incapsula) and outgoing traffic (responses sent to clients from Incapsula) are taken into account.

    • Traffic between Incapsula and your origin servers is not taken into account. This includes:

      • The fetch to the origin server for missing response content.

      • The traffic sent back from the origin server to be cached in Incapsula.

    • Both cached bits and non-cached bits are taken into account.

    • Blocked traffic is not taken into account. Blocked traffic includes blacklisted traffic, L3/4 DDoS traffic, L7 DDoS traffic, bad bots, security rules, and others.

    • Traffic is aggregated across all services (IP Protection, Name Server Protection, Website Protection, and Infrastructure Protection).

    • For sites that are protected by Website Protection as well as IP Protection or Infrastructure Protection, the traffic for those sites is only counted once in the overall calculation of aggregated traffic.

  • Total traffic in each bucket is then divided by 300 to convert it to bits per second (bps) format.

  • At the end of the month, starting on the billing date, the 5% of buckets with the most bps are dropped, and the highest bps rate of the remaining buckets represents the 95th percentile value for the account.

  • The calculation is performed separately for always-on services and on-demand services.

  • The calculation for on-demand services takes into account only those time periods during which traffic was diverted to Incapsula.

    For example, if traffic was diverted to Incapsula for one week out of the entire month, the calculation drops the top 5% of the traffic during that week.


How is the 95th percentile calculated for non-web traffic?

Calculation of non-web traffic is performed in exactly the same way as web traffic. Usage is calculated across all IPs and/or IP ranges into 5-minute buckets which are aggregated with all other services.

The calculation is performed separately for always-on services and on-demand services (separate buckets and aggregation).

Where can I see the 95th percentile calculation?

In the Incapsula Management Console, on the sidebar, click Management > Subscription.

Note: Bandwidth calculation displayed on the Subscription page includes both incoming (visitors > Incapsula) and outgoing (Incapsula > visitors) traffic.

Alternatively, bandwidth usage displayed in the Management Console's Network and Infrastructure Dashboards reflects ingress traffic only (visitors > Incapsula). The dashboards display peak values for the selected time period.

The Subscription page displays statistics for the last 30 days. It does not correspond directly to your billing cycle. For example, if your billing cycle begins on the first of the month and you are looking at the Subscription page on the 15th, the statistics displayed for the last 30 days include both part of the previous billing cycle and part of the current billing cycle.

Can I view past billing data?

You can download bandwidth history, which includes the current billing cycle and two previous billing cycles.

In the bandwidth history, the current billing cycle shows usage from the start of the billing cycle through the moment you run the report. For example, if the billing cycle begins on the 1st of the month and you run the report on July 23rd, the report will cover July 1-23.

If traffic has been high until this point in the current billing cycle, you may see usage that’s over the limits of your purchased plan. For example, suppose you are on a 100 Mbps plan, but bandwidth usage for the current billing cycle shows 120 Mbps. This means that the 95th percentile calculation covering July 1-23 is 120 Mbps. But if usage during the remaining days of the billing cycle (from July 24-31) is lower, the final calculation for the month will be lower, and possibly within the limits of your 100 Mbps plan.

What happens when an account exceeds its plan?

At the beginning of each billing cycle, the system checks whether or not the account exceeded its plan in the last billing cycle. In the event of an overage, a notification will be sent to the account's owner.

What happens if a site under Web Protection is also protected by IP Protection or BGP-based Infrastructure Protection? Will Incapsula charge for the site's traffic twice?

No. In such a case Incapsula will subtract that specific site’s traffic from the total accumulation in the calculation of the 95th percentile.

How does the cumulative model, used by other CDNs, work?

Many CDNs use the cumulative model for clean traffic billing. Some offer both cumulative and burstable alternatives. The cumulative model is calculated according to the total bytes that are “consumed” during a given month. It is usually presented in either GB or TB.