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List:       ipfilter
Subject:    Re: Wish list...
From:       Jefferson Ogata <ogata () pmpro ! com>
Date:       1997-12-16 15:33:11
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Jon Zeeff wrote:
> 
> To do web load balancing correctly, you need to do "session-level" load
> balancing.  Ie, you can't switch a user back and forth between two
> web servers for each tcp connection.  The breaks many statefull
> web sites.  Most distributors use some type of timer that says all
> traffic from this ip address goes to this server for some number of
> minutes after idle.
> 
> > This is interesting, but if I'm interpreting your message correctly, you are
> > talking about connection-level load balancing. I was asking about packet-level
> > load balancing, such as you get with SLiRP. This allows you to bind a number of

I understand that; that's why I'm trying to clarify that I'm asking about a
different problem. Web load balancing is altogether different from what I was
talking about, and it is not handled by the strategy I was referring to.
Bandwidth sharing over multiple links, on the other hand, is handled by what
I am talking about, and is not handled by connection-level load balancing, except
at times when all interfaces are saturated. If you tried to apply my strategy to
web load balancing, you would break not only stateful web sites -- you'd break TCP
completely.

Am I making myself clear? Here it is one more time, just in case:

How hard would it be to have ip-filter collect a group of interfaces into a
single logical interface, then fastroute each outgoing packet to the interface
that has carried the least traffic, while doing NAT on all the interfaces in
the group using the same IP address? This is not a strategy for balancing
compute load over multiple machines; it is a strategy for ganging interfaces
to get multiple-link bandwidth. This is load balancing of individual links, not
machines.

Anyone have any comments on this? It's something I've wanted to look into for a
long time, but haven't had any time for. I was hoping someone else might have done
some work in this area. I am currently using SLiRP with three 28.8 modems and get
up to 7KB/s incoming. I was hoping to lasso ip-filter into doing the same thing for
outgoing traffic. I've hacked dp-4.0 in the past for this, but that was under SunOS
4.1.3_U1 and my Magma 4-serial SBUS card just didn't work right under SunOS.

-- 
Jefferson Ogata             pmpro, inc           ogata@pmpro.com
   Q: How many engineers does it take to change a light bulb?
   A: One.

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