95th percentile billing, explained — with a calculator

How the 95th percentile is calculated

1. 01SampleEvery five minutes, read the port’s byte counters and turn the difference into a rate. A 30-day month gives 8,640 samples per direction.
2. 02SortOrder the month’s samples from lowest to highest.
3. 03Discard the top 5%Drop the highest 432 of 8,640 — about 36 hours of the month. Bursts that fit inside that window cost nothing.
4. 04Bill the next oneThe highest remaining sample is the 95th percentile. Anything above the commit is overage, priced per Mbps.

A worked example — the calculator’s defaults. A customer commits to 100 Mbps. Their traffic follows a daily curve that peaks around 130 Mbps, and backup jobs push about 600 Mbps for 30 hours in total across the month. Those 30 hours fit inside the 36 that are discarded, so the backups vanish from the bill: the 95th lands at 128.9 Mbps, and the customer pays for 28.9 Mbps over the commit. Let the backups run 37 hours instead and the 95th jumps to 571.8 Mbps — 471.8 over the commit. One more hour of bursting, sixteen times the overage.

From switch port to invoice line, without a spreadsheet

FluxBilling polls each IP transit customer’s switch port every five minutes over SNMP, drops repeated samples, and at the close of the cycle computes the 95th exactly as the calculator above does. Overage above the commit becomes an invoice line — or a proforma, if that is how you bill — with progressive tiered rates if your contracts use them. Direction is set globally, per product or per service: inbound, outbound, the sum, or the higher of the two at each sample.

The same service can bill commit-and-burst, per-GB transfer with an included allowance, or a flat port instead. It sits on the same records as the rack, the IP allocation and the rest of the colocation invoice.