> It's not just AS_PATH, a lot of the reason so many duplicate updates > occur (nearly 50% of all updates at times, and often more during the > busiest times) is because on the other end implementations don't keep > egress advertisement state per attribute (e.g., if cluster_list length > just triggered an internal transition then a new update is sent to > external peers with no new information because the determining > internal attributes are stripped before transmitting the new update), > yet those *prefixes* might well be suppressed as a result of the > implementation and/or network architecture on the other end of the BGP > connection. > > Then you couple what Joe was pointing out, where intermediate nodes > with consistently unstable links or "paths" result in penalizing an > entire prefix, not just the unstable paths, and it makes for more > brokenness than benefit when route flap damping is employed. > > It's not that people haven't studied and understand why this occurs, > the issue is that implementation optimizations seem to always win out > today over systemic state effects (i.e., that "be conservative in what > you send" thing doesn't seem to apply in practice, unfortunately).
might some of this be that the implementations use router-id to fill in an unconfigured rr cluster-id? randy
