Route leaks — when a BGP announcement propagates beyond where it should, often black-holing traffic — have historically been guarded by hand-written operator filters. Jordan and Riley walk through how RFC 9234 moves that protection into the protocol itself, using the BGP Role capability (neighbors negotiate provider/customer/peer up front) and the Only-to-Customer (OTC) attribute (routes get stamped so compliant routers auto-reject leaked ones), enforcing "valley-free" routing automatically. The catch from Cloudflare's real-world measurement: some large Tier-1 networks strip the OTC attribute as they forward routes, undermining protection for everyone downstream — a classic internet collective-action problem where the safety property only fully holds if the backbone cooperates. Source: BGP Role model: tracking the adoption of RFC 9234 — The Cloud ...