[ofa-general] [RFP] support for iWARP requirement - activeconnectside MUST send first FPDU

[Felix Marti]

> -----Original Message-----
> From: general-bounces at lists.openfabrics.org [mailto:general-
> bounces at lists.openfabrics.org] On Behalf Of Kanevsky, Arkady
> Sent: Tuesday, October 23, 2007 6:26 PM
> To: Glenn Grundstrom; Sean Hefty; Steve Wise
> Cc: Roland Dreier; interop-wg at lists.openfabrics.org; OpenFabrics
> General
> Subject: RE: [ofa-general] [RFP] support for iWARP requirement -
> activeconnectside MUST send first FPDU
> 
> This is still a protocol and should be defined by IETF not OFA.
> But if we get agreement from all iWARP vendors this will be a good
> step.
[felix] This will not work with a Chelsio RNIC which follows the IETF
specification by a) not issuing a 0B RDMA Write to the wire and b)
silently consuming an incoming 0B write. Therefore 0B RDMA Writes cannot
be 'abused' for such a synchronization mechanism. I believe that the
mentioned apps adhering to the iWarp requirement do a 'send' from the
active side and only have the passive side issue RDMA ops once the
incoming send has been received. I would guess that following a similar
model is the best way to go and supported by all iWarp vendors
implementing the IETF spec.


> If we can not get agreement on it on reflector lets do
> it at SC'07 OFA dev. conference.
> 
> Arkady Kanevsky                       email: arkady at netapp.com
> Network Appliance Inc.               phone: 781-768-5395
> 1601 Trapelo Rd. - Suite 16.        Fax: 781-895-1195
> Waltham, MA 02451                   central phone: 781-768-5300
> 
> 
> > -----Original Message-----
> > From: Glenn Grundstrom [mailto:ggrundstrom at NetEffect.com]
> > Sent: Tuesday, October 23, 2007 9:02 PM
> > To: Sean Hefty; Steve Wise
> > Cc: Roland Dreier; interop-wg at lists.openfabrics.org;
> > OpenFabrics General
> > Subject: RE: [ofa-general] [RFP] support for iWARP
> > requirement - activeconnect side MUST send first FPDU
> >
> > > > That is what I've been trying to push.  Both MVAPICH2 and
> > > OMPI have been
> > > > open to adjusting their transports to adhere to this
requirement.
> > > >
> > > > I wouldn't mind implementing something to enforce this in
> > > the IWCM or
> > > > the iWARP drivers IF there was a clean way to do it.  So
> > far there
> > > > hasn't been a clean way proposed.
> > >
> > > Why can't either uDAPL or iW CM always do a send from the active
to
> > > passive side that gets stripped off?  From the active side,
> > the first
> > > send is always posted before any user sends, and if
> > necessary, a user
> > > send can be queued by software to avoid a QP/CQ overrun.  The
> > > completion can simply be eaten by software.  On the passive
> > side, you
> > > have a similar process for receiving the data.
> >
> > This is similar to an option in the NetEffect driver.  A zero
> > byte RDMA write is sent from the active side and accounted
> > for on the passive side.  This can be turned on and off by
> > compile and module options for compatibility.
> >
> > I second Sean's question - why can't uDAPL or the iw_cm do this?
> >
> > >
> > > (Yes this adds wire protocol, which requires both sides to support
> > > it.)
> > >
> > > - Sean
> > >
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