[Beowulf] Channel bonding, again

Kilian CAVALOTTI kilian at stanford.edu
Fri Oct 12 09:53:06 PDT 2007

Hi all,

On Friday 12 October 2007 04:57:50 am Henning Fehrmann wrote:
> On the other hand, one needs to trunk (HP calls it trunking) the
> ports on the switches. We tried it on HP and Cisco switches. 
> The switch collects the packages of the trunked ports and
> redistributes them according to a level 2 or level 3 hash policy.
> Here starts the problem: the packages are coming with the same IP-
> and MAC-address. The switch gets confused and, furthermore, the
> switch wants to do the work which is already done by the node.

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].

[1] http://en.wikipedia.org/wiki/Link_Aggregation_Control_Protocol
[2] http://www.cisco.com/en/US/products/ps6566/products_feature_guide09186a008071860b.html
[3] http://www.dell.com/downloads/global/power/ps1q06-20050254-Holmes.pdf
[4] http://www.linuxhorizon.ro/bonding.html
[5] http://www.freebsd.org/cgi/man.cgi?query=lagg&apropos=0&sektion=4&manpath=FreeBSD+7-current&format=html
[6] http://www.daemon-systems.org/man/agr.4.html


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