The BGP Clock and the BGP Observatory: Hunting Stuck Routes#

Antonis Chariton, Cisco

• Why: Stuck BGP routes (withdrawals lost to router bugs) silently keep traffic flowing toward dead paths — and after a route goes stale, nobody notices. This provides both a permanent public measurement beacon and a free detection tool anyone can point at their own network.
• What: Follow-up to the RIPE 89 study (which found prefixes still stuck in RIBs months after withdrawal, despite being RPKI Invalid). The BGP Clock announces time-encoded prefixes on a fixed schedule: IPv6 2a0d:3dc1:NNNN::/48 indexed by 10-minute period since New Year (recycled yearly), and IPv4 147.189.(216+N).0/24 by hour-of-day modulo 8, announced at XX:00 and withdrawn at XX:10. The BGP Observatory is a free, no-login service that detects and surfaces stuck routes, searchable by AS. RFC 9687 attempts to reduce the impact but needs vendor support.
• How: Beacon prefixes are originated from a dedicated AS (AS4601, moving to AS210312); operators can sanity-check their own RIBs directly (show route for the beacon prefixes) or use the Observatory's automated analysis.
• Where applicable: Any operator or researcher; the phenomenon's prevalence depends on the vendor/bug mix in the forwarding path, so absolute numbers will shift over time — the value is the standing instrument, not a single result.