[166266] in North American Network Operators' Group
Re: comcast ipv6 PTR
daemon@ATHENA.MIT.EDU (Barry Shein)
Tue Oct 15 14:38:41 2013
From: Barry Shein <bzs@world.std.com>
Date: Tue, 15 Oct 2013 14:30:03 -0400
To: Jimmy Hess <mysidia@gmail.com>
In-Reply-To: <CAAAwwbW5ZFTzEJskXcGmRpPZuT0y=jA02cwOX1wkUzJa2+mUoQ@mail.gmail.com>
Cc: John Levine <johnl@iecc.com>, NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On October 14, 2013 at 22:18 mysidia@gmail.com (Jimmy Hess) wrote:
> On Mon, Oct 14, 2013 at 10:01 PM, Barry Shein <bzs@world.std.com> wrote:
>
>
> > > 2001-0db8-85a3-0042-1000-8a2e-0370-7334.example.com
> > >?
> >
> >
> No... it's not a lot of work; the problem is, it's maybe worth even
> less than the amount of work involved though.
>
> What piece of information is being expressed there that would not be
> expressed by a NXDOMAIN response?
That your host won't be rejected, typically by email servers, in an
RDNS check.
It's a little strange in a way, the very existence of an RDNS response
has become a policy trigger, no matter what it is.
> Assuming the user is residential ".example.com" pertains to the ISP,
> not the hostname at that IP address. The ISP's info is accessible via
> services such as WHOIS-RWS
>
>
> How about some wildcard PTR record ?
>
> *.3.a.5.8.8.b.d.0.1.0.0.2.ip6.arpa PTR unnamedhost.example.com.
>
> It's equally useless; and conveys equally limited information about the
> host.
That really depends on what you believe is useless (or useful.)
If it lets the client send email to AOL (as one example) that might be
useful.
The information it conveys is that this IP address merits an RDNS
response for some reason, and policy is determined on that fact.
> However, at least it doesn't generate spurious records that are just (IP
> repeated).(domain)
Well, as I said, you're setting a different standard, that the host
name returned in an RDNS query be of some meaning to a human or
possibly a program.
Its mere existence is considered very meaningful on the net, whatever
it is.
--
-Barry Shein
The World | bzs@TheWorld.com | http://www.TheWorld.com
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