Round Robin

David Nolan vitroth+ at
Tue Nov 7 15:10:46 UTC 2006

--On Tuesday, November 07, 2006 07:39:32 -0700 Bill Larson 
<wllarso at> wrote:

> There is a DNS "solution" available for this situation.  Take a look
> at "lbnamed", a "load balanced" DNS server.  It is NOT BIND, written
> in Perl, and is fairly old.  I'm sure that there should be security
> issues involved with trying to use this.
> If your DNS server provides dynamic DNS capabilities, you could use
> some external script to run "nsupdate" to remove and add your servers
> to DNS as needed.

Carnegie Mellon's Netreg provides a similar functionality via a perl 
process (also called lbnamed) that issues dynamic dns updates to a bind 
server based on server metrics.

> There are other, non-DNS, load balancing systems that may be much
> better solutions.  These operate by manipulating the network routing
> of a single address.  If you are really serious about this need, then
> this type of solution would be a much better solution, but costly.

True IP load balancer aren't necessarily expensive.  The commercial ones 
are, but there are open source options.  Linux Virtual Server is free, and 
pretty reliable. you just need some hardware to run it on.  The commercial 
solutions tend to provide "layer 4" balancing, i.e. they're application 
proxies, but there are open source solutions in this area as well, see 
perlbal, the load balancer written by the folks behind livejournal, used by 
livejournal and others.

-David Nolan
 Network Services
 Carnegie Mellon University

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