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SubjectRe: Poor Performance for ethernet bonding
Thomas Davis wrote:
>
> Ben Greear wrote:
> >
> > Couldn't the bonding code be made to distribute pkts to one interface or
> > another based on a hash of the sending IP port or something? Seems like that
> > would fix the reordering problem for IP packets.... It wouldn't help for
> > a single stream, but I'm guessing the real world problem involves many streams,
> > which on average should hash such that the load is balanced...
> >
>
> Cisco etherchannel does this, by XOR'ing the dest address with the
> source address, AND'ing with # of interfaces (limiting you to a power of
> 2), and then using the number to determine what channel to use.
>
> Now, you end up in a 4 way Etherchannel, all the traffic going down one
> channel, and the none going down the other three. Does that sound like
> a balanced solution?

If Cisco can't do a balanced hash, that doesn't mean the idea is bad,
it just means they implemented it poorly. I would think that
something as simple as: src_ip_port % num_devices would give a
fairly even spread. I'm sure you could get fancier and take other
fields (dst_ip_port) into account in your hash.


--
Ben Greear <greearb@candelatech.com> <Ben_Greear@excite.com>
President of Candela Technologies Inc http://www.candelatech.com
ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear
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