[Rdma-developers] Re: [openib-general] OpenIB and OpenRDMA: Convergence on common RDMA APIs and ULPs for Linux

Fri May 27 12:48:19 PDT 2005

At 10:25 AM 5/27/2005, Sukanta ganguly wrote:
>Mike,
>    I am not sure I do understand what your were trying
>to communicate. Let me try and decode this. My basic
>point was to respond to Venkata's response about
>complete offload without any interaction with the host
>system. I disagree with that in its totality as I
>think there are dependencies and that needs to be
>specified in a formal manner, i.e. in the specs, so
>that we do not have multiple proprietary interafaces
>which change and application users have to change this
>consumption based on individual implementations.
>    And you just brought up the reasons why what I was
>saying seemed to be justfied. Did I read that
>correctly?

You understand correctly.  We need defined interface points where other 
subsystems can choose to interact with the RDMA infrastructure.  Further, 
there is a set of issues that have yet to be addressed, e.g. that go to how 
a customer uses / manages the attached fabrics and how their tool chain is 
impacted or not.

Mike

>Thanks
>SG
>
>--- Michael Krause <krause at cup.hp.com> wrote:
>
> > At 06:40 AM 5/27/2005, Sukanta ganguly wrote:
> > >Venkata,
> > >    How will that work? If the RNIC offloads RDMA
> > and
> > >TCP completely from the Operating System and does
> > not
> > >share any state information then the application
> > >running on the host will never be in the position
> > to
> > >utilize the socket interface to use the
> > communication
> > >logic to send and receive data between the remote
> > node
> > >and itself. Some information needs to be shared.
> > How
> > >much of it and what exactly needs to be shared is
> > the
> > >question.
> >
> > Ok.  It all depends upon what level of integration /
> > interaction a TOE and
> > thus a RNIC will have with the host network stack.
> > For example, if a
> > customer wants to have TCP and IP stats kept for the
> > off-loaded stack even
> > if it is just being using for RDMA, then there needs
> > to be a method defined
> > to consolidate these stats back into the host
> > network stack tool
> > chain.  Similarly, if one wants to maintain a single
> > routing table to
> > manage, etc. on the host, then the RNIC needs to
> > access / update that
> > information accordingly.  One can progress through
> > other aspects of
> > integration, e.g. connection management, security
> > interactions (e.g. DOS
> > protection), and so forth.  What is exposed again
> > depends upon the level of
> > integration and how customers want to manage their
> > services.  This problem
> > also exists for IB but most people have not thought
> > about this from a
> > customer perspective and how to integrate the IB
> > semantics into the way
> > customers manage their infrastructures, do billing,
> > etc.  For some
> > environments, they simply do not care but if IB is
> > to be used in the
> > enterprise space, then some thought will be required
> > here since most IT
> > don't see anything as being "free" or self-managed.
> >
> > Again, Sockets is an application API and not how one
> > communicates to a TOE
> > or RDMA component.  The RNIC PI has been proposed as
> > an interface to the
> > RDMA functionality.  The PI supports all of the
> > iWARP and IB v 1.2 verbs.
> >
> > Mike
> >
> >
> > >Thanks
> > >SG
> > >
> > >--- Venkata Jagana <jagana at us.ibm.com> wrote:
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > rdma-developers-admin at lists.sourceforge.net
> > wrote on
> > > > 05/25/2005 09:47:00
> > > > PM:
> > > >
> > > > > Venkata,
> > > > > Interesting coincidence: I was talking with
> > > > someone (at HP) today
> > > > > who knows substantially more than I do about
> > > > RNICs.
> > > > > They indicated RNICs need to manage TCP state
> > on
> > > > the card from userspace.
> > > > > I suspect that's only possible through a
> > private
> > > > interface
> > > > > (e.g. ioctl() or /proc) or the non-existant
> > (in
> > > > kernel.org)
> > > > > TOE implementation. Is this correct?
> > > > >
> > > >
> > > > Not correct.
> > > >
> > > > Since RNICs are offloaded adapters with RDMA
> > > > protocols layered on
> > > > top of TCP stack, they do maintain the TCP state
> > > > internally but
> > > > it does not expose to the host. RNIC expose only
> > > > RNIC Verbs interface
> > > > to the host bot not TOE interface.
> > > >
> > > > Thanks
> > > > Venkat
> > > >
> > > > >
> > > > > hth,
> > > > > grant
> > > > >
> > > > >
> > > > >
> > > >
> >
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