Subject: RE: [rddp] Options and Markers

From: [email-masked]
Date: Mon, 14 Apr 2003 16:42:25 -0400

> > My take-away from the San Francisco RDDP meeting was that there
> > was rough consensus for mandating markers,
> 
> There was certainly not unanimous consensus.  I guess it's 
> David's call as to what constitutes rough consensus.

It is, and the issue of whether to mandate markers or not was
not part of the discussion in the San Francisco meeting - that is
very much an open issue.

> > So I guess you are questioning the value of the markers as a desired
> > element of RDDP/TCP architecture.  Again, I thought we're past that 
> > question.

We did get past that question - but notice the use of "desired" as
opposed to "mandatory" in the way that Mallikarjun phrased it - things
that aren't "desired" should not be put into a specification, and
markers clearly are "desired".  The conclusion from SF is that markers
will need to be specified with a 512 byte interval.  This discussion
is about "optional to use" and "optional to implement for receivers",
which are different issues.

> > Let's not assume that a commercially available VI-based adapter
> > running at relatively low speeds, compared to what this WG is
> > trying to design for, defines the "architectural best practices"
> > for RDDP/TCP.  I would be much more convinced about this VI-based
> > design if there is "running code" for 10G.

That appears perpetuate the incorrect assumption that high speed
hardware implementations are the only thing worth making design
decisions for.  Please see my previous comments on this topic.

Thanks,
--David
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David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
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From: Caitlin Bestler <[email-masked]>
Date: Mon, 14 Apr 2003 23:01:05 -0500

> which are different issues.

This is a very important distinction.

The strongest justification for markers is that they enable low-memory
high-speed RNICs. I believe the case has been made for allowing such RNICs to
mandate markers on connections sent to them.

I also believe that the case has been made that for memory-rich receivers, that
the markers are a nuisance and a slight bandwidth waste.

That leave the real issue being assessing which is the greater imposition:

-- forcing senders to support both marker and no-marker mode.
-- forcing memory-rich receivers to implement markers.

The primary virtue of the latter is that it avoids options. Allowing recievers
to mandate "no markers" is clearly superior for pure-software RDDP stacks
written on top of sockets.
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