A complete traffic path from source to destination typically passes through multiple networks, with different AS numbers. This is reflected in the traceroute results. If the Outage detection is enabled in the IRP configuration, the system gathers network performance information for all traceroute hops over which the traffic passes to the remote networks. Next, each hop is translated into AS numbers. In case any network anomalies are detected on a specific ASN, then this ASN and the immediate neighbor ASN are declared a problematic AS-pattern. The system then re-probes the prefixes that pass through this AS-pattern. In case the issue is confirmed, all related prefixes are rerouted to the best performing alternate provider.
The Outage detection uses a statistical algorithm for selecting the best routing path. Rerouting will occur for all the prefixes that are routed through the affected as-pattern, despite their current route.
Several improvements-related reports need to indicate the original route for a specific prefix. This value is taken from the last probing results for this prefix, even if the results are outdated (but not older than 24h). Since the outage-affected prefixes are rerouted in bulk by as-pattern, in some cases the reports can show the same provider for both the old and the new route.