> On Tue, Jun 26, 2007 at 02:44:41PM +1000, Mark Andrews wrote:
>
> > > [RFC1912] suggests that it is an operational or
> > > configuration error not to have matching PTR and A records.
>
> > Every address should have a PTR which gives the cannonical name
> > of the host which in turn has a matching address record.
> >
> > It is a bad idea to say for the to be a PTR for every ownername
> > of a address record. It doesn't take too many A records, which
> > all have the same address, before you exceed the DNS protocol
> > limits with multiple PTR records.
>
> The proposed text is intended to go in section 2, which is background
> for the document. I believe that the draft is actually a softening of
> the language in RFC1912, partly for the reasons you state. There is
> text consitent with what you are saying in section 3.3:
>
> It is possible for there to be multiple PTRs at a single reverse tree
> node. In extreme cases, these multiple PTRs could cause a DNS
> response to exceed the UDP limit, and fall back to TCP. Such a case
> could be one where the advantages of reverse mapping are exceeded by
> the disadvantages of the additional burden. This may be of
> particular significance for "mass virtual hosting" systems, where
> many hostnames are associated with a single IP.
>
> Now that I look at this, however, it's not really correct, given
> EDNS0. So, I have two questions:
>
> 1. Does the text from section 3.3 address your concerns about the
> proposed additional text in section 2 ("Background")?
>
> 2. Can you (or anyone else) suggest a better way of phrasing the
> "multiple PTR" paragraph to account for EDNS0 as well?
EDNS really doesn't change it. You can still exceed the
limits of what can be put into EDNS/UDP packets. You
can also exceed what can be put into a {E}DNS/TCP message.
I've seen the later occur plenty of times.
> Thanks,
> A
>
> --
> Andrew Sullivan 204-4141 Yonge Street
> Afilias Canada Toronto, Ontario Canada
> <[EMAIL PROTECTED]> M2P 2A8
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>
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Mark Andrews, ISC
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