Re: [LARTC] many ways to do load balancing (or not?)

["William L. Thomson Jr." <support@obsidian-studios.com>]

On Fri, 2002-11-22 at 04:28, Andreas Hasenack wrote:
>
> Sure. When I said "packet count" before I was thinking about something
> along the lines of real traffic balancing, that is, the router somehow
> remembering how many packets it sent to each route and choosing the
> less used one.

That would be one step closer to true load balancing but I do not thing
would work for the other end the client. Instead it just splits
requests/lookups and does not completely load balance traffic or
packets. 

It is very easy to have uneven loads. For this one day I will look into
QoS when the time is right, hoping it may be able to help even out the
load? At least from the inside.

Once again from the outside load balancing is done via DNS.

> > It would be getting responses from an IP it was not expecting response
> > from. I would imagine each side to send redirects, and all sorts of
> > problems. Like it receiving every other packet and dropping the packets
> > in between.
> 
> And breaking stateful firewalls.

Yep

> > If during a file transfer the route cache is flushed, there is the
> > possibility of the rest of the packets going out a different interface.
> 
> Uh oh... It shouldn't be that simple, what about that 60s timeout for
> the cache? It's very likely to occur during a file transfer.

Well that's more a worse case scenario like manually flushing the cache.
I believe the cache gc algorithm takes in consideration routes that are
currently in use. So lookups do not occur during a transfer?

I have not really seen this to be a big problem. Although I do not have
any large files being downloaded, and if I did it could cause problems
there.

But so far I have not had any problems along those lines.

> > Neither does it perfectly or with intelligent algorithms. Neither allow
> > you to use all paths for a single transfer.
> 
> Only things like MPPP I guess, for example, or channel bonding, or TQL.

Yes, but I believe each of those requires special configurations on both
ends, client and ISP.

> > So if you have two 1.5 mbs connection, you do not end up with a 3.0 mbs
> > line. You do have one internal gateway for both, and if one goes down
> > the other can be used. So you do have redundancy, and both lines can be
> > used to serve difference requests to different places.
> 
> So it's more like redundancy/HA with a best effort towards balancing.

Yes, or in other terms. My need was a single gateway for my servers
although I have two ISPs. The amount of load balancing you get it about
the same as the amount of redundancy. You get a partial solution to
both, but not a complete solution.

-- 
Sincerely,
William L. Thomson Jr.
Support Group
Obsidian-Studios Inc.
439 Amber Way
Petaluma, Ca. 94952
Phone  707.766.9509
Fax    707.766.8989
http://www.obsidian-studios.com

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