Re: LC Comments on "considerations" scaling analysis

[Eric Rosen <erosen at cisco.com>]

If you are going to recommend one scheme over another based on a scalability
analysis, then the analysis must  take into account all the scaling factors.
You do not have the option  of saying "I didn't consider memory utilization,
that's out of scope", or "I didn't consider sparse mode, that's out of scope
(even though it is an important factor in virtualyl every deployment)".

Further,  if  you want  to  draw any  conclusions  whatsoever  based on  the
analysis of a small subset of  the scalability issues, you have to show that
that subset contains the bottleneck issues.  If the MVPN bottleneck is PE-CE
PIM, then you can't say "I'm only considering PE-PE PIM, PE-CE PIM is out of
scope". 

It also helps if the analysis  uses a measure of "resource utilization" that
has some practical meaning.  The sum of the number of cycles expended by all
routers has no practical  meaning at all; if it did, no  one would ever have
heard of such notions as "distributed computing" or "datagram networks".

If  you do  a scalability  analysis without  attending to  any of  this, the
analysis  is simply  irrelevant,  if it  happens  to be  correct within  its
limited scope.

Of course, if you are doing  a purely theoretical analysis, with no intended
practical application, then of course you can focus in on any isolated issue
that you choose.  However, I don't  think the IETF is the proper publication
venue for that.

A  further  issue  is that  the  analysis  provided  in  Appendix A  of  the
"considerations" draft is not correct even within its limited scope, for all
the reasons  I have detailed  in a prior  message.  These mostly have  to do
with the  failure to  properly understand the  effects of  join suppression.
But I'm not sure it's worthwhile to repeat all those points again as part of
the same last call.

I will just  reiterate my request for  Appendix A to be removed  and for any
recommendations depending upon it to be removed.