nanog mailing list archives
Re: DNS pulling BGP routes?
From: Tom Beecher <beecher () beecher cc>
Date: Thu, 7 Oct 2021 10:12:42 -0400
But, the reality is that it is impossible to correctly recognize server is unavailable or to correctly withdraw routes only when server is unavailable.
Not true at all. On Thu, Oct 7, 2021 at 9:50 AM Masataka Ohta < mohta () necom830 hpcl titech ac jp> wrote:
William Herrin wrote:This is quite common to tie an underlying service announcement to BGP announcements in an Anycast or similar environment.Yes, that is a commonly seen mistake with anycast.You don't know what you're talking about.I do but you don't.If your anycast node stops receiving updated data and you can't reach any of the other nodes to check whether they're online, 99 times out of 100 this means a local failure of some sort.Yes. In case of DNS, if expiration period of a zone is passed without successful check of the current most zone version, unicast or anycast name servers stop responding requests for the zone. But, it has nothing specifically to do with anycast. As there are other name servers with different IP addresses, there is no reason to withdraw routes. So?You withdraw the node's announcement so that you don't serve bad data to the end user.That will only introduce new failure modes of mismatches between server availability and server reachability and is a bad idea.That's what happened here -Yes, facebook did wrong thing to actively withdraw routes.Simply turning themselves off, instead of withdrawing the routes, would result in suboptimal performance.This time, facebook is saying that they could not reach their name servers even though the servers were perfectly working. How much performance, do you think, facebook enjoyed? A lot less than "suboptimal", I'm afraid. > And 99 times out of 100, not doing > one or the other would cause rather than prevent an outage. That is a commonly seen misconception wrongly assuming that server routes were withdrawn if and only if the server is unavailable. But, the reality is that it is impossible to correctly recognize server is unavailable or to correctly withdraw routes only when server is unavailable. Masataka Ohta
Current thread:
- Re: Facebook post-mortems..., (continued)
- Re: Facebook post-mortems... Bjørn Mork (Oct 05)
- Re: Facebook post-mortems... Masataka Ohta (Oct 06)
- Re: Facebook post-mortems... Bjørn Mork (Oct 06)
- DNS pulling BGP routes? Michael Thomas (Oct 06)
- Re: DNS pulling BGP routes? J. Hellenthal via NANOG (Oct 06)
- Re: DNS pulling BGP routes? Jared Mauch (Oct 06)
- Re: DNS pulling BGP routes? Blake Dunlap (Oct 06)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 06)
- Re: DNS pulling BGP routes? William Herrin (Oct 07)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 07)
- Re: DNS pulling BGP routes? Tom Beecher (Oct 07)
- Re: DNS pulling BGP routes? Bjørn Mork (Oct 07)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 07)
- Re: DNS pulling BGP routes? William Herrin (Oct 07)
- Re: DNS pulling BGP routes? Mark Tinka (Oct 07)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 07)
- Re: DNS pulling BGP routes? William Herrin (Oct 07)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 07)
- Re: DNS pulling BGP routes? William Herrin (Oct 07)
- Re: DNS pulling BGP routes? Masataka Ohta (Oct 07)
- Re: DNS pulling BGP routes? Sabri Berisha (Oct 07)