[dns-operations] who cares about RA bit

Mark Andrews marka at isc.org
Fri Jun 17 03:58:33 UTC 2011

In message <508280403.02570 at cnnic.cn> <003101cc2c9c$86add000$94097000$@cn>, "zh
anglikun" writes:
> On Friday, June 17, 2011 7:41 AM, Mark wrote:=20
> > Stub resolvers expect recursive service.  Some answers get
> > mis-interpretted if they don't get recursive service.  Some resolver
> > libraries will skip servers that do not set RA in responses to
> > queries with RD set.  If the caller of the library has requested
> > recursive service then the library has to ensure that the answer
> > returned is complete and the only way it can determine that is to
> > look for RA.  If they don't see RA they move onto the next nameserver
> > listed in resolv.conf or the equivalent.
> A more specific question, should RA bit be set when the query is =
> rejected by a pure resolver? (caused by ACL, or query is Update, XFR, =
> etc. ), or if it is set, is there any bad point?

I would still set it if appropriate for the client.

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

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