Subject: Re: [Roll] Review and concerns - the missing text in the post

From: "David E. Culler" <[email-masked]>
Date: Tue, 09 Dec 2008 14:33:06 -0800

I would like to emphasize a few points in the thread - Working Group 
Last Call: draft-ietf-roll-protocols-survey-02

Phil correctly observes that we reached consensus on the process long 
ago.  After taking feedback on a early version of the draft we agreed on 
(1) the definition of the universe of candidates (so the process would 
terminate), (2)  that we would build a tableau of candidates versus 
criteria and (3) that we would conduct a detailed analysis in order to 
obtain a rough scoring of pass, fail, ?.  We discussed and consensed on 
the criteria.  These are fundamentally related to the charter - routing 
on (a) low-power and (b) lossy links.  We debated small discrepancies in 
the analysis since the summer IETF.  We recognized that such analysis 
and such criteria were imperfect, but necessary.  We all recognized that 
scaling characteristics  are essential  and yet the constants  also 
matter.  We recognized that even passing all the criteria may not be 
sufficient for having a completely satisfactory solution.  Thus, they 
are viewed as necessary, but not sufficient.  We recognized that there 
would be regimes where the constants all worked out, even if the general 
case did not.  But, it would be fruitless for the whole discussion to 
degenerate into debates about the exact value of innumerable tuning and 
scaling constants.

Some of the concerns center on the difficulty of meeting these 
criteria.  Indeed, the working group was formed because there are real 
problems to solve.  The application routing requirements drafts make 
clear that the criteria are real, not spurious.  So, whether they hard 
or not they serve well to define the goal.  At the same time, there are 
several existence proofs of solutions in the market and in the research 
community that meet these criteria or are very very close.  So they do 
not appear to be "holy grails" but rather pragmatic guidelines for solid 
design and engineering effort.

Other comments observe that the criteria do not address every possible 
concern.  Indeed, they are viewed as necessary but not sufficient.  At 
the same time, they go a very long way to addressing the full problem, 
as substantiated by the application drafts.  So it appears that they do 
serve to reasonably define a "sweet spot" goal.  Meeting the criteria 
makes it extremely likely that real needs can be met with reasonable 
engineering of solutions developed around this goal.

Many other concerns recognize that modifications of existing protocols 
in a manner that is focused on these criteria would make them far more 
suitable.  That suggests that the criteria and the analysis in the draft 
serve their goal.  We are not chartered to consider such modifications 
until after this ID is done.

Some concerns recognize that there are protocols outside the defined 
universe that should be considered and that appear to be far better 
suited to meeting the criteria than the set of IETF protocols that were 
considered - since those protocols were developed without these 
criteria.  Again, that suggests that the criteria are a reasonable 
guide, that they do not appear to be unobtainable, and that the analysis 
has provided a suitable guide.

None of the comments seem to be claiming that there is a solution within 
the universe that we were chartered to consider that meets the criteria.

These were the reasons that we reached consensus on the draft, its 
criteria, and its analysis.  We could spend forever on the debate, but 
if it does not change the conclusion it is only time lost. 

At best it might be that if the criteria were suitably weakened there 
might be an existing solution that met those relaxed criteria.  Again, 
no one has proposed such a lowering of the bar and it is unclear that 
such lowering would meet the application requirements.

These were the factors that led to consensus, thus enabling us to move 
forward.
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