Returning one address from a RRset

Sven Ingebrigt Ulland SvenI.Ulland at iu.hio.no
Mon May 1 02:04:19 UTC 2006


How can I modify the BIND source code to only return one address from
a resource record set (a set of A records for a cluster of
load-balanced web servers, in this case)? I've tried finding the
relevant code, but came up short, close to lib/dns/rdata*. Also, there
does not seem to be an option for this in named.conf, perhaps for
obvious reasons.

The reason I'd like to do this, is to try to figure out how it affects
the ability of DNS to act as a load balancing dispatcher. It is part
of a small student research project which aims to quantify the various
aspects of DNS-based load balancing. I'm aware of the controversy
regarding load balancing and DNS, explained in some detail at
http://www.isc.org/index.pl?/sw/bind/docs/bind-load-bal.php but I'd
still like to find out not only why it is a bad combination, but /how/
bad it is.

On a sidenote, it appears www.amazon.com uses an approach similar to
the one explained above -- try a 'dig @207.171.167.7 a www.amazon.com',
and it returns one address each time, from a set of two (or more?).

Also, I'm aware of the BIND-DLZ projects, which would allow for the
same kind of behaviour, but I'd like to avoid the latency impact of a
dynamical back-end.

kind regards,
sven



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