[176508] in North American Network Operators' Group
Re: Comcast residential DNS contact
daemon@ATHENA.MIT.EDU (Niels Bakker)
Wed Dec 3 07:04:50 2014
X-Original-To: nanog@nanog.org
Date: Wed, 3 Dec 2014 13:04:42 +0100
From: Niels Bakker <niels=nanog@bakker.net>
To: nanog@nanog.org
Mail-Followup-To: nanog@nanog.org
In-Reply-To: <7A6352F1-6373-4720-A0AD-6CDFFF47002D@gmail.com>
Errors-To: nanog-bounces@nanog.org
* shortdudey123@gmail.com (Grant Ridder) [Wed 03 Dec 2014, 12:54 CET]:
>Both of Google’s public DNS servers return complete results every
>time and one of the two comcast ones works fine.
>
>If this is working by design, can you provide the RFC with that info?
An ANY query will typically return only what's already in the cache.
So if you ask for MX records first and then query the same caching
resolver for ANY it won't return, say, any TXT records that may be
present at the authoritative nameserver.
This could be implementation dependent, but Comcast's isn't wrong, and
you should not rely on ANY queries returning full data. This has been
hashed out to tears in the past, for example when qm**l used to do
these queries in an attempt to optimise DNS query volumes and RTT.
-- Niels.
