Re: comcast ipv6 PTR

[Barry Shein <bzs () world std com>]

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

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