On Thursday, 25 June 2020 18:29:03 UTC Paul Wouters wrote: > On Thu, 25 Jun 2020, Mukund Sivaraman wrote: > > For whoever is interested, this is a description of a pattern of queries > > noticed at busy public resolvers that has led to issues in at least 4 > > different sites in the last 2 months. > > > > The current revision is a work in progress. We are still developing some > > mitigations for NIOS, and some more introductory text also has to be > > added. > > I would add a more explicit section on using prefetching of frequently > asked queries, which mitigates (eliminates) the period when an answer is not > available in the cache.
i'm sorry in advance for anybody who is now hearing this for the 100th time. please don't pre-fetch. feel free to pre-discard; TTL is a maximum, and if you want to randomly subtract from TTL upon every reuse, you'll remain compliant. if the data turns out to be important it'll return. but prospective pre-fetch means you may be creating network load for no purpose -- the data may not come back again, or if it does, it may have changed, in which case you don't want the stale stuff that pre-fetch would have brought you. this solves the thundering herd problem but without creating new problems. the goal is de-synchronization. random subtractions to TTL in cache accomplishes it. -- Paul _______________________________________________ DNSOP mailing list [email protected] https://www.ietf.org/mailman/listinfo/dnsop
