[openib-general] IPoIB broadcast MC group membership

[Fabian Tillier]

On 22 Feb 2006 06:32:29 -0500, Hal Rosenstock <halr at voltaire.com> wrote:
> On Wed, 2006-02-22 at 02:40, Fabian Tillier wrote:
> > On 2/21/06, Greg Lindahl <lindahl at pathscale.com> wrote:
> > > On Tue, Feb 21, 2006 at 08:17:02PM -0800, Fabian Tillier wrote:
> > >
> > > > The node joining or creating the multicast group doesn't need to
> > > > specify the rate - the SA can figure out the rate to use based on the
> > > > requestor (for creation), or validate that the requestor supports the
> > > > existing group's rate (for joining).
> > >
> > > Um, but that gets back to my point: I want 1X, 4X SDR, and 4X DDR
> > > nodes running IPoIB to share a multicast group. Are you saying this
> > > can be done by making the group a 1X group? Or that it's impossible
> > > to have such a group? Or that everyone would have to drop to 1X to
> > > make such a group?
> >
> > You'd have to make the group 1X.  Note that the group being 1X doesn't
> > limit unicast traffic to 1X rates, since the rate for unicast traffic
> > would be set based on the rate reported in the path records for the
> > various endpoints.
>
> It does, however, limit all other (IB) multicast groups in that
> partition to the same rate as the IPoIB broadcast group. That may be the
> correct choice of the admin (and 1x nodes would be refused).

I agree that 1X nodes are likely erroneous, and it's fine (and
probably preferable) for an admin to cause these to be refused.  I
started this thread with the intent on figuring out how to distinguish
refusal from some other failures, so that IPoIB could log the
appropriate event and a system administrator could identify that there
was a bad link in the fabric.  The IB spec doesn't provide for a
mechanism to do that, and Hal and I will work to change that.

- Fab