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

[Sean Hefty]

>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.

Hmm...  I'd like to find a way to avoid using the same QKey for everything, but
maybe it's not any worse than what we have with IP anyway.  I guess if we know
if a UD QP will not join a multicast group, we can use any QKey, but use a well
known QKey if it will join a multicast group.

What would happen in the following situation:

App 1:
Creates QP with QKey=22
Joins multicast group 1 with QKey=33

App 2:
Creates QP with QKey=44
Joins multicast group 1
Sends to multicast group but with QKey=22

- Sean