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Re: [DNSOP] Measuring DNS TTL Violations in the wild

Mukund Sivaraman <muks@isc.org> Sat, 02 December 2017 14:39 UTC

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Date: Sat, 02 Dec 2017 20:09:25 +0530
From: Mukund Sivaraman <muks@isc.org>
To: Ólafur Guðmundsson <olafur@cloudflare.com>
Cc: "Wessels, Duane" <dwessels@verisign.com>, dnsop <DNSOP@ietf.org>, "Giovane C. M. Moura" <giovane.moura@sidn.nl>
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Subject: Re: [DNSOP] Measuring DNS TTL Violations in the wild
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On Fri, Dec 01, 2017 at 05:16:47PM +0000, Ólafur Guðmundsson wrote:
> On Fri, Dec 1, 2017 at 5:02 PM, Wessels, Duane <dwessels@verisign.com>
> wrote:
> 
> >
> > > On Dec 1, 2017, at 8:38 AM, Ólafur Guðmundsson <olafur@cloudflare.com>
> > wrote:
> > >
> > > I strongly disagree with your "terminology", TTL is a hint about maximum
> > caching period, not a demand or a contract.
> >
> > You say its just a hint.  If you put a TTL of 1 hour on your data, and I
> > have a recursive name server that reuses it for 2 hours, 12 hours, 5
> > days... thats okay?
> >
> > If its just a hint then we are we spending all this effort on "serve
> > stale"?
> >
> > DW
> >
> >
> Strictly speaking yes, it is the same as when a Secondary does not update
> the zone for a long time.

An authoritiative server operator knows what the consequence of setting
SOA RDATA fields is. It isn't the same as a cache extending TTL as it
sees fit, in spite of the loose coherency among primary and secondaries.

I don't agree a downstream cache has authoritiative say about extending
TTLs (except exceptional circumstances where the authority is
unreachable ~serve-stale).

		Mukund

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