RE: [Tsvwg] RE: iSCSI: No Framing

["Douglas Otis" <dotis@sanlight.net>]

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.

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.

Doug


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