[176514] in North American Network Operators' Group
Re: Comcast residential DNS contact
daemon@ATHENA.MIT.EDU (Brian Rak)
Wed Dec 3 10:49:43 2014
X-Original-To: nanog@nanog.org
Date: Wed, 03 Dec 2014 10:46:49 -0500
From: Brian Rak <brak@gameservers.com>
To: Jared Mauch <jared@puck.nether.net>, Stephen Satchell <list@satchell.net>
In-Reply-To: <1FCB5596-71AA-4D0C-9CBB-CE561898800B@puck.nether.net>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
Shouldn't everyone be on IPv6 these days anyway ;)
On 12/3/2014 10:28 AM, Jared Mauch wrote:
> So have A record queries. Do you filter those as well?
>
> Jared Mauch
>
>> On Dec 3, 2014, at 9:08 AM, Stephen Satchell <list@satchell.net> wrote:
>>
>>> On 12/03/2014 04:04 AM, Niels Bakker wrote:
>>> * 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.
>> At the ISP I consult to, I filter all ANY queries, because they have
>> been used for DNS amplification attacks.
