Does replies to existing domain name contain additional section

[Barry Margolin]

In article <388356D0.5F47E0A at india.hp.com>,
Praveen Kumar Amritaluru  <praveen at india.hp.com> 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.

When the answer or authority sections contain NS or MX records, the
additional section may contain the A records for the target hostnames in
those records.

>         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.

Yes.  That's the most common case.

The purpose of the additional section is to answer the queries that are
likely to come next.  So if you tell someone an MX record, they're going to
need to look up its A record in order to use it.  If you have the
information in your cache or authoritative data, you include it to save
them the trouble and time delay of querying again.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.