Subject: negative caching support

From: bert hubert <[email-masked]>
Date: Thu, 3 Oct 2002 13:15:12 +0200

Hi,

RFC 1034 mentions the following about negative response caching:

 The method is that a name server may add an SOA RR to the additional
 section of a response when that response is authoritative.  The SOA must
 be that of the zone which was the source of the authoritative data in
 the answer section, or name error if applicable.  The MINIMUM field of
 the SOA controls the length of time that the negative result may be
 cached.

However, bind 8 and 9 add the SOA RR to the authority section.

In the interest of interoperability, what do you suggest an authoritive DNS
implementation should do? Follow the RFC or bind?

Regards,

bert hubert
PowerDNS

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From: Jim Reid <[email-masked]>
Date: Thu, 03 Oct 2002 17:57:01 -0700

>>>>> "bert" == bert hubert <[email-masked]> writes:

    bert> So this appears to be a good idea. Sadly, DENIC for example
    bert> demands a 40.000 second SOA minimum which is a bit much for
    bert> negative caching.

Why? Long TTLs are a very good thing IMO, even for negative answers.
Large TTLs should only present a problem when people don't plan and
co-ordinate their DNS changes very well. For instance, by dropping the
TTL on a server a decent interval before the box gets renumbered.

And anyway, what's stopping someone changing their SOA values after
DENIC has done their pre-registration check and delegated the zone?

---

From: Peter Koch <[email-masked]>
Date: Fri, 04 Oct 2002 10:30:57 +0200

> Why? Long TTLs are a very good thing IMO, even for negative answers.

while there have been different statements even for the effectiveness of
positive caching in the past, the gain of negative caching lies within
shorter time frames. It helps with 'insisting' resolvers and applications
(at least that's what I've seen on a server with lots of IN-ADDR.ARPA
zones).

> TTL on a server a decent interval before the box gets renumbered.

Sure, but you can't decrease the TTL on particular negative answers in
advance.

> DENIC has done their pre-registration check and delegated the zone?

Nothing, unfortunately.

-Peter

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From: "Marcos Sanz/Denic" <[email-masked]>
Date: Fri, 4 Oct 2002 12:26:17 +0200

>     bert> demands a 40.000 second SOA minimum which is a bit much for

Actually, any value between 180 and 345600 is accepted.

> DENIC has done their pre-registration check and delegated the zone?

Nothing. That´s the reason why I am a defender of unannounced periodical
checkings..