switch for channel bonding

Paul Nowoczynski pauln at psc.edu
Fri Aug 18 12:24:29 EDT 2000


trunking, link aggregation, channel bonding, are all the same.  i think
the best method is to use 2 switches. the problem that i've seen on both
cisco and intel switches is that the recv streams are not divided between
the 2 recv'ing interfaces.  so don't expect to see ~180 mbits/sec
between a point-to-point sender/receiver application if you're using the
switch's trunking capability,  you'll need multiple streams to get that.
but if you can wire your cluster so that interface0 goes to one switch and
interface1 goes to another switch then you could get good point-to-point
bandwidth.
paul

On Fri, 18 Aug 2000, Bogdan Costescu wrote:

> 
> Hi,
> 
> AFAIK Cisco calls "channel-bonding" what others call "trunking". I have
> used Cisco 5000 series' "channel-bonding" and BayNetworks 350-24T's
> "trunking" facilities and they worked just the same. Whatever it's called
> it's supposed to do this: allow bundling of several physical links into a
> logical one. To do this, they require that all the NICs at the other end
> have the same MAC (Ethernet address).
> 
> It's not possible to split one packet among the physical links, but
> different packets can go through different links. The decision of which
> link to use for sending a packet is completely up to the device (switch or
> Linux host, not the NIC) and there may be different strategies. For
> example the Linux "channel-bonding" module presently uses a Round-Robin
> strategy, where the packet "i" is sent through the link i % n (i modulo
> n), where "n" is the number of physical links available. At the Rx end,
> the packets from "ethx" are all sent to the bonding module (in the order
> they were received), and the upper levels just see the packets coming from
> "bond0".
> 
> The bonding facility was introduced in the 2.2 series earlier this year 
> and was recently modified. It can be used to bond 2 or more NICs (the
> maximum number is not a limit of the bonding module AFAIK) - usually the
> switch limits the number of physical links that can be bonded (4 for some
> Cisco switches and for BayNetworks 350). You can bond different brands of
> NICs (e.g. a 3Com, a DEC-based and a EEPro), the bonding module doesn't
> care about this; however, for getting good results, the bonded NICs should
> be similar in performance. And no, you don't need any patches for the
> network drivers; I suppose that one of the things that was present in the
> patches that you mention was the abillity to set the Ethernet address;
> nowadays, all the network drivers that I know of allow this.
> 
> To come back to the original question: there are quite a lot of switches
> that allow "channel-bonding"/"trunking"/whatever is called. I know of
> quite a lot of the Cisco switches, the 3900 switches from 3Com,
> BayNetworks 350 and 450, some Intel switches. Usually, this facility is
> mentioned in the white-paper of the switch, so just searching on the web
> sites of these (and maybe other) manufacturers might give you the answers;
> also usually they write a lot about how beneficial this facility can be to
> you, so it's quite hard to miss it.
> Mr. Thomas Davis (tadavis at lbl.gov) wrote in the README accompanying the
> bonding module that he would like to put together a list of switches
> reported to work with it (based on the feedback from the users...)
> However, I don't know if this list exists.
> 
> Sincerely,
> 
> Bogdan Costescu
> 
> IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
> Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
> Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
> E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
> 
> 
> 
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