4 ms·

But then it is the DNS that had to propagate from the now accessible authoritative servers.

• Hikikomori 5y ago
  Shouldn't take long once they are up and responding again?
  • WorldMaker 5y ago
    I'd assume it is a cache invalidation problem at that point: from my lay understanding BGP probably needs to busts caches on a withdrawal to keep traffic from going to black holes and prevent DDoS attempts, but probably has to wait for TTL timeouts to cache new routes (and those TTLs are going to vary by whatever cache systems the other ASes are running not the timing of Facebook's AS sending the new [old] routes.).
    • Hikikomori 5y ago
      BGP doesn't really cache routes, though you can configure routers to hold a route for some time if a peer times out, but this is only used in special cases and usually not something you would want your router to do with routes to other networks. If a router gets a withdrawal for a route it will remove the route from the table without waiting. This is a feature and important part of how BGP acts in case of problems and how it can self heal quickly, there's no point in caching a route when that path is not working anymore and usually there's a backup path.