Load Balancing under Linux

[Gerald Combs]

On Thu, 25 Apr 2002, Jonathan Hutchins wrote:

> How much participation is required from the "other end" to do load balancing
> and failover?  Those of use considering using something like RoadRunner and
> SWB DSL as a backup probably wouldn't get any cooperation at all from Bell
> or TWC, so it would have to be something we could implement without the
> ISP's help.

It depends on the type of load balancing and failover you want to do.  If
you want to make sure the world can get to your mail server no matter
what, you need to exchange routing information with more than one provider
so that they can advertise your network to the rest of the world, and thus
provide diverse paths for the world to get to your server.  As an example,
go go http://nitrous.digex.net/mae/mae-lg.html and do a BGP query for
131.107.3.125 (one of Microsoft's mail servers).  A whacking great pile of
AS (Autonomous System) paths is returned.  By looking up the various ASNs
at www.arin.net, we find that Microsoft peers with UUNet, Genuity, Level
3, Sprint, Cable & Wireless, AT&T, and AboveNet.  This sort of setup
requires a fair amount of effort, resources, and cooperation with
upstream providers.

On the other hand, if you just want to make sure your company has enhanced
outbound connectivity you can use the various tricks described in previous
messages without the knowledge, approval, or interaction of your
providers. However, the solutions that I saw (and suggested) seem a little
kludgy for my tastes.  There ought to be a more straightforward way to
point iptables, ipfilter, squid et al at separate interfaces, and then
tell them to dynamically distribute outbound load across them.

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