intelligent selection of forwarders?

James Ralston qralston+ml.bind-workers at
Thu Aug 15 20:16:22 UTC 2002

On Wed, 14 Aug 2002, Cricket Liu wrote:

> > The 4th edition of "DNS and BIND" contains this comment on forwarder
> > selection (page 270):
> > 
> >     On BIND 8.2.3 name servers, you don't need to list forwarders
> >     more than once.  These name servers don't necessarily query
> >     the forwarders in the order listed; they interpret the name
> >     servers in the list as "candidate" forwarders and choose which
> >     one to query first based on roundtrip time, the time it took
> >     to respond to previous queries.
> > 
> > (The last sentence of the first paragraph doesn't parse; 
> I beg to differ.  [...]

Ok, I see now the meaning that was intended.  (I wasn't expecting an
appositional explanation of roundtrip time; it seemed like it was
describing a second measurement that BIND was conducting in order to
discriminate among servers which had approximately the same network

> > So, my question: what version of BIND 9 implements the more
> > intelligent forwarding?  If the answer is "none", then is there an
> > estimate when (as in, what version) this feature will be added?
> The answer is none.  Maybe someone at Nominum can give you an
> estimate of when the feature will be added.

Thanks for the info.

Honestly, we don't care a whole lot about the load-balancing aspect of
this feature (i.e., BIND finding the best forwarder to use).  What we
*do* care about is having rapid failover from a failed forwarding

James Ralston, Information Technology
Software Engineering Institute
Carnegie Mellon University, Pittsburgh, PA, USA

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