about the additional section

[Mark Andrews]

In message <CAA3U4eOSoZ46zjzQtRH0EgMWKmGRqxb0oc9TmR1p=wfF44WHVg at mail.gmail.com>
, =?UTF-8?B?6aOO5rKz?= writes:
> 2011/9/1 Daniel McDonald <dan.mcdonald at austinenergy.com>:
> > On 8/31/11 10:13 PM, "风河" <shorttag at gmail.com> wrote:
> >
> >> Hello,
> >>
> >> I found that some queries have got the response which has additional
> >> section, but some haven't.
> >> For example, this query with www.google.com got the answer with
> >> additional section set:
> >>
> >> $ dig www.google.com
> >> ;; MSG SIZE Â rcvd: 236
> >> $ dig www.google.com
> >>
> >> ;; MSG SIZE Â rcvd: 220
> >
> >> My question is under what condition the nameserver answers the query
> >> with additional section set?
> >
> > When there is sufficient space for the additional information in the 
> packet,
> > it is sent.
> >
> 
> But as you see, both of my queries have the size of 200+, less than 512 
> bytes.
> So why they didn't include the full additional sections?

Named doesn't return records tagged as additional in the additional
section.  This stops the propogation of bogus records.  Note there
is no requirement for additional records to be added ever.  Glue
records are not additional records even though they are in the
additional section.

> Thanks.
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org