Detailed explanation can be found below.
https://blog.thousandeyes.com/centurylink-level-3-outage-analysis/ From: NANOG <nanog-bounces+lguillory=reservetele....@nanog.org> on behalf of Baldur Norddahl <baldur.nordd...@gmail.com> Date: Wednesday, September 2, 2020 at 12:09 PM To: "nanog@nanog.org" <nanog@nanog.org> Subject: Re: [outages] Major Level3 (CenturyLink) Issues *External Email: Use Caution* I believe someone on this list reported that updates were also broken. They could not add prepending nor modify communities. Anyway I am not saying it cannot happen because clearly something did happen. I just don't believe it is a simple case of overload. There has to be more to it. ons. 2. sep. 2020 15.36 skrev Saku Ytti <s...@ytti.fi<mailto:s...@ytti.fi>>: On Wed, 2 Sep 2020 at 16:16, Baldur Norddahl <baldur.nordd...@gmail.com<mailto:baldur.nordd...@gmail.com>> wrote: > I am not buying it. No normal implementation of BGP stays online, replying to > heart beat and accepting updates from ebgp peers, yet after 5 hours failed to > process withdrawal from customers. I can imagine writing BGP implementation like this a) own queue for keepalives, which i always serve first fully b) own queue for update, which i serve second c) own queue for withdraw, which i serve last Why I might think this makes sense, is perhaps I just received from RR2 prefix I'm pulling from RR1, if I don't handle all my updates first, I'm causing outage that should not happen, because I already actually received the update telling I don't need to withdraw it. Is this the right way to do it? Maybe not, but it's easy to imagine why it might seem like a good idea. How well BGP works in common cases and how it works in pathologically scaled and busy cases are very different cases. I know that even in stable states commonly run vendors on commonly run hardware can take +2h to finish converging iBGP on initial turn-up. -- ++ytti
