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Case study · holding a contract to its numbers

An ISP contract, checked by measurement rather than by complaint

minute probes · attribution ladder · monthly SLA report · measured 2026-09-24

Problem

Under EU rules a fixed-line contract states minimum and normally available speeds, and a claim needs a significant, continuous or recurring shortfall. That is a statistical argument. A screenshot of one slow speed test is not evidence, and neither is a feeling that the line was down.

Action

A probe every minute walks a ladder: the router, then two independent public anchors, and only when both fail, the ISP's own gateway. Each outage lands on the layer that caused it. A speed test runs every two hours. Once a month a report goes out with the verdict against the contract.

Outcome

25,000+ probes, 0 minutes that count as an ISP outage. Of the 17 minutes without internet, 16 were the house's own network and one the fibre link, and each is recorded as exactly that, so none pads the provider's score in either direction.

The detail worth keeping: the monthly report goes out even when the month was clean. A report that only arrives when something is wrong cannot be told apart from a monitor that has stopped running; one that always arrives turns its own absence into the alarm.

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