Re: [Tsvwg] RE: iSCSI: No Framing

["Brian F. G. Bidulock" <bidulock@openss7.org>]

Douglas,

On Wed, 06 Feb 2002, Douglas Otis wrote:

> Brian,
> 
> > Lloyd,
> >
> > On Wed, 06 Feb 2002, Lloyd Wood wrote:
> >
> > > On Wed, 6 Feb 2002, Brian F. G. Bidulock wrote:
> > >
> > > > What is lost by throwing layering out the window?
> > >
> > > modularity, ease of understanding, and portability.
> >
> > Modularity can be acheived without layering.  The entire
> > field of OOAD proves this.
> >
> > Ease of understanding is acheived through accurate
> > interface description.  Again OO shows this.
> >
> > Portability can also be acheived through OO approaches.
> >
> > The classical layering of communications functions
> > into functional groupings is not a necessary condition
> > for any of these benefits.
> 
> Unlike a typical play dough program, this stuff is more like working with
> concrete.  A portion of each application demanding a direct placement
> feature would be included in hardware or intelligent adapters if using FIM
> and TCP, or framing and TCP, for the most part.  SCTP allows layering for
> this "clean modularity" needed if one is to design an adapter that need not
> understand the complexities and structures of every application that desires
> this function.  The adapter interface only needs to understand SCTP and not
> the application.  By using the unordered delivery mode, a shim would be able
> to implement generalized structures for including Direct Data Placement or
> even a full implementation of RDMA.  It would be possible for more elaborate
> interfaces to built upon this foundation, but at least this establishes the
> modularity, ease of understanding, and portability desired, if one is going
> to start working in concrete.

Not necessarily...  Nowadays entire OS's and applications are embedded on
the adapter.  The adtapter can have full knowledge of all applications
which it supports and provide only higher level application interfaces
to app blades.  This is the preferred architecture for scalability and
redundancy as well as proving a clean separation between applications
and the application engine.

If some want to agree on how this embedding is going to occur with some
vestige of interoperability, what does it matter?  Would not your time be
better spent furthering DDP/SCTP?  It is certainly not the first time that
IETF has had competing approaches: ultimately the market decides.

--brian

> 
> Unlike the case with FIM and TCP, this would introduce NIC devices that will
> be forever sensitive to even minor changes to structures employed in these
> applications and the desire for this feature does not even begin to end at
> just one application.
> 


-- 
Brian F. G. Bidulock
bidulock@openss7.org
http://www.openss7.org/