[openib-general] [Fwd: RE: IB mcast question]

[Steve Wise]

On Tue, 2006-08-15 at 16:12 -0400, Hal Rosenstock wrote:
> On Tue, 2006-08-15 at 15:59, Roland Dreier wrote:
> >  > This is what I was referring to.  I'm really not familiar with IP multicast
> >  > beyond what I read in a book while coding the RDMA CM.  It sounds like we might
> >  > be able to use the QKey as the port number for the QP to mimic the behavior.
> > 
> > I don't see how this could work-- to mimic IP, an app has to be able
> > to multicast a datagram to multiple destination ports using the same
> > multicast group.  Since IB multicast groups have a Q_Key associated,
> > the only way this could work is if all QPs and MCGs share one Q_Key.
> 
> Isn't it all QPs on the same MCG need to share one Q_Key ?
> 

>From my experimentation, only the qkeys of the QPs need match.  The MCG
qkey is only needed for sending to the group.

Am I confused? (often the case :)