Re: Load Balancing over several interfaces

From: Henrik Nordstrom <>
Date: Mon, 12 Oct 1998 00:12:11 +0200

Karl Schaffarczyk wrote:

> the difficulty is this... the outgoing requests all go via the
> 2Mb link.. the source IP dictates the return path.
> Thus, to alter the routing, one must change the outgoing address.

Yes, and the outgoing address is determined by which interface (real
or virtual) that is used for your default route. Not a very hard
problem in my opinion.

> Does anyone have any good ideas on implementation of such a daemon?
> If a patch could be written for something like this, then it would
> prove *very* popular in Australia, where Telstra Internet charge
> ridiculous prices for bandwidth.

1. Determine a way to measure when the link is saturated (SNMP,
packet/byte rate counting or whatever that is suitable)

2. Find yourself two network configuraions. One where the bidirectional
link is used for all traffic, and one where it is only used for outgoing
traffic. You must be able to make both these configurations to go on
from here.

3. Set up a host that can handle both configurations simoultaneously for
incoming traffic. As two different IP addresses is needed you may
require two physical network cards depending on your OS and it's
aliasing and routing capabilities.

4. Build a simple monitoring package using whats learnt in step 1 and 3
to switch between the two communication methods depending on networ

Sounds quite straigt forward to me, provided that you can solve step 1

I don't think something like this belongs inside Squid. It is more
suitable outside Squid as it is a networking problem and not directly
related to Squid functions.

Henrik Nordström
Spare time Squid hacker
Received on Sun Oct 11 1998 - 15:18:15 MDT

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