[Beowulf] Channel bonding, again

Carsten Aulbert carsten.aulbert at aei.mpg.de
Sun Oct 14 12:19:33 EDT 2007


Hi all,

Kilian CAVALOTTI wrote:
> I think LACP (802.3ad) [1] is supposed to address these issues: it
> allows swicthes to negotiate an automatic configuration of individual
> ports by exchanging LACP packets with the peer. From the switch 
> standpoint, a LACP port group is considered as a single logical port, 
> which kind of alleviate those multiple-ports-same-address problems, 
> while conserving the advantages of increased bandwidth and failover if 
> one individual link fails.
> 
> LACP is supported by Cisco [2] and Dell [3] switches, and for the peer 
> side, by the Linux bonding module (mode 4) [4], the FreeSBD lagg(4) 
> driver (>= 6.2-STABLE) [5] and by NetBSD agr(4) [6].
> 

I don't know from the top of my head which versions we have used, but
our problem with LACP was that the switch (mostly ProCurve 2900, but i
think the Cisco 4948 behaved similarly, but that I would need to
cross-check) was using only a single of the available two or four lines
to the node for a single connection. Thus a node could handle two
different 1 GB/s connections at the same time and reaching almost 2 Gb/s
in total, but we  never saw a single connection using all the available
bandwidth.

That was the reason our student came up with this VLAN trick.

Cheers

Carsten
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