Does replies to existing domain name contain additional section

[Kevin Darcy]

Praveen Kumar Amritaluru wrote:

> Hi ,
>
>          I am not clear regarding the additional section in the replies to
> queries
> sent to  nameservers.
>
>         When will the reply from nameserver contain RRs in the additional
> section.
>
>          Is it valid to have RRs in the additional section when the hostname
> queried
> is found in the domain for which the nameserver is authoritative of.
>
>         Can anyone clarify this.
>
>         Thanks in advance for your insights.

BIND typically puts A records there which are associated with records in the
other sections, e.g. for previously-mentioned MX records, NS records,
SRV records, etc. According to the code, it looks like KEY records could also
be returned in the additional section, although I've never seen this in
practice. I don't believe the authoritativeness of the answer has any bearing
on the contents of the additional section.

But you shouldn't really rely on anything in particular being returned in the
additional section, since I believe the RFC's don't mandate anything in this
regard, and not everyone runs BIND. Also, if the response packet gets too big,
BIND will jetison the additional section in order to prevent truncation.


- Kevin