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Datasources

BGP

Active Probing

Network Telescope

Outage Detection

Detection Criteria

BGP

Active Probing

Darknet

Outage Severity Scores

Alert Area

To quantify the severity of an outage, we use a concept we call Alert Area, which takes into account both the magnitude of the outage and the duration of the outage. The alert area is computed by multiplying the relative drop (i.e. ((history - current) / history) * 100) by the length of the outage (in minutes). All alert tables in IODA show Alert Area values as per-datasource outage severity scores.

Overall Score

While we perform outage detection on a per-datasource basis, we use multiple datasources to gain confidence about an outage. To do this, we compute an Overall Score by multiplying the Alert Area scores for each data source that triggered an alert. We multiply Alert Area scores together (rather than summing them) to give weight to outages that have been detected through multiple datasources.

Caveat: While the "Overall Score" values given in the alert tables reflect a multiplication of the total alert area for each data source, the "Overall Score" value shown in the "Outage Severity Levels" visualizations is instead the sum of the overall score values for each minute in the time window. That is, an overall score is computed for each minute by multiplying together the alert areas for that minute, and then these per-minute overall scores are summed to give the total shown when hovering over a country or region.