[openib-general] APM support in openib stack

[Or Gerlitz]

On 1/4/07, Tang, Changqing <changquing.tang at hp.com> wrote:

> > >     + use IB PORT GIDs at your initial mpi init exchange
> > >     + issue IB SA Path query via libibsa (which does not exist)
> >
> > likely multipath query if you want APM

> Yes, we want to have APM as well.

The RDMA CM is about to be enhanced to support IB APM where for now
you would need to provide the alternate path from some "out of rdma
cm" band means. But in the future an enhancemnt of the IB SM would
allow the RDMA CM to provide you with the alternate path as well.

> > There are other possibilities here too using inband (IB) exchanges.
> > libibsa is not that far away either. What is your time frame ?

> Is it possible to have it in OFED 1.2 ?

I don't see any much advantge for you with libibsa over hard coding a
path, ie use dynamic GIDs/LIDs and static or hacked setting for the
other path record fields.

> > Also, you would make more work if iWARP support is of
> > interest as well.
> > It comes "for free" or at least "for cheap" if the RDMA CM
> > approach is taken.

> We understand that, but we hope to have a connect/accept style IB
> connection setup, without IPoIB involved,
> like HP-UX IT-API(similar to uDAPL without underlying IP support), it
> works with multiple cards.

CQ,

Please note that to have iWARP support you **must** use the rdmacm to
establish the RDMA connection.

This is b/c unlike IB, iWARP connection can't be hard wire manually.
First a TCP connection is established and then this connection is
moved to RDMA. Since you cann't hard wire a TCP connection you must
use the IWARP CM etc for that. So bottom line, using the RDMA CM would
give you IB and iWARP support and you can't support iWARP without
it...

Or.