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

[Andreas Hasenack <andreas@conectiva.com.br>]

Em Fri, Nov 22, 2002 at 10:05:25AM -0800, William L. Thomson Jr. escreveu:
> > 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.

I just found this patch, has anybody already played with it?

ftp://sliepen.warande.net/pub/eql/patch-2.4.18-2.gz

Excerpt:

Load balancing needed a slight adjustment to the unpatched linux kernel,
because of the route cache. Multipath is an option already found in the old
2.1.x kernels. However, once a packet arrives, and it matches a multipath
route, a (quasi random) device out of the list of nexthops is taken for its
destination. That's okay, but after that the kernel puts everything into a
hash table, and the next time a packet with the same source/dest/tos arrives,
it finds it is in the hash table, and routes it via the same device as last
time. The adjustment I made is as follows: If the kernel sees that the route
to be taken has got the 'equalize' flag set, it not only selects the random
device, but also tags the packet with the RTCF_EQUALIZE flag. If another
packet of the same kind arrives, it is looked up in the hash table. It then
checks if our flag is set, and if so, it deletes the entry in the cache and
has to recalculate the destination again.

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