[dns-operations] Questions on DNS Flag day 2020 proposal

Mark Andrews marka at isc.org
Tue Jun 18 03:14:29 UTC 2019

> On 18 Jun 2019, at 12:11 pm, Mark Delany <b9w at charlie.emu.st> wrote:
>> STD13 doesn't say glue as optional and not being able to fit glue
>> into a referral response should result in TC=1 being set.
> Do you mean for auths only or intermediaries as well?
> I'm thinking of caches and proxies which accept a TC=0 answer from their
> upstream but find they have to truncate this answer to suit their downstream
> clients.

Caches don’t return referrals.  Proxies need to behave as if they are an
authoritative server.

> Do intermediaries reliably know which RRSets are "required" (to use rfc2181
> parlance) or should they take a safe/simplistic approach and arbitrarily set
> TC=1 on all downstream truncation? That would certainly cover your use-case.

And should be safe.

> A brief examination suggests that intermediaries are all over the shop in this
> regard but obviously mostly "work" so long as the Answer section is non-empty or
> TC is set. In spite of this (or perhaps because of this) guidance for all
> components would be helpful.
> Mark.
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org

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