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Re: Slashdot: Providers Ignoring DNS TTL?
On Fri, 22 Apr 2005, Dean Anderson wrote: > On Thu, 21 Apr 2005, Stephen J. Wilcox wrote: > > > On Wed, 20 Apr 2005, Dean Anderson wrote: > > > > > On Wed, 20 Apr 2005 firstname.lastname@example.org wrote: > > > > > > > > I'd rather expect this sort of behavior with anycasted servers... > > > > > > > > Where do you see any connection between anycast and ignoring DNS TTL? Or is > > > > this just part of your usual rant against anycast DNS service? > > > > > > The data he showed isn't necessarilly "ignoring ttl". If there are multiple > > > anycasted caching servers behind a specific IP address, then those several > > > cache's will each have a different state. Since, [as I > > > > I fail to see the correlation still.. anycasted caches should all be operating > > independently getting their DNS data from authoritative sources. > > > > If at any point one of them uses a TTL that it has not received from the > > authoritative source it is ignoring the ttl, where does anycast get involved > > with this particular problem? > > The queries produce different data, but none of the data is inconsistent > if there are different caches responding on the same address. Here is the > original description: (slightly reformated with roman numerals) > > (I) I ran a query for a name in a zone I control that has a five minute > TTL on 184.108.40.206. The first query came up with 5 minutes. > (II) I quickly made a change to the zone. > (III) Thirty seconds after the initial query, I try > again...err... and come up with the change. Hmm... Not caching at all? > (IV) Another 30 seconds and I get the change, with 5m TTL. > (V) Thirty seconds later, I get the original response with appropriately > decremented TTL. > (VI) Another thirty seconds, I get the change, with 4m TTL. > > Here is the detailed anycast explanation: > (I) Cache 1 gets answer to query X? = Y > (II) Authority changes X? to Z > (III) Cache 2 gets answer to query X? = Z > (IV) Cache 3 gets answer to query X? = Z > (V) Cache 1 responds > (VI) Cache 3 responds > > No TTLs were ignored. Ok gotcha, and you point seems valid except aiui the previous post was concerning providers who are actually overriding the TTL eg your zone has a 5m ttl, the provider caches it but sets TTL to 10 days. i think this thread forked quite early :) Steve