[Iccrg] Heresy recapped

[Matt Mathis]

My "heresy" proved to be rather anticlimactic.  Although there was a spirited 
discussion about the nature of fairness*, there was no real discussion about 
my position about rescinding the TCP-friendly paradigm.  Does this mean there 
is agreement in this group?

I would like to nudge the iccrg to go on to the next step:  What do we need to 
do to phase out the TCP-friendly paradigm?

I had a separate conversation with the original authors of "TCP-Friendly", 
Jamshid Mahadavi and Sally Floyd [1], where we came to realize that there 
still needs to be some litmus test for acceptable protocol behavior.

There is a huge amount of work needed here: we do not even have a formal 
definition of congestion collapse, much less any methods to test if a given 
congestion control algorithm might be subject to collapse.  Is it sufficient 
for all users/protocols to merely optimize their own good put?  There is an 
entire arena of research here that has been waved away by "its TCP-friendly, 
so we don't need to worry about ...."  All past questions potentially need to 
be re-opened.

In the short term, we can always evaluate protocols and algorithms on a 
case-by-case basis.  In doing so we are likely to discover the underlying 
principles.  I guess the very short term question is what, if anything, should 
we say to tcpm about BIC and CTCP?

Note we probably need a warning labels on some protocols: "This protocol (or 
application) will not politely share the network with other users, unless 
network itself enforces appropriate sharing.  In environments without the 
required controls in the network it is likely to cause lockout or other 
extreme unfairness."

*) I specifically did not define fairness because I believe that my comments 
apply independent of the fairness model.  Fairness is very important to ISPs, 
and their conversations with both their customers and their equipment 
suppliers.  Except for algorithms where people want to allocate header bits or 
code points, I don't believe that these conversation need the participation of 
standards organizations because reasonable differences in implementation do 
not have any affect on interoperability.  Furthermore, it surprises me that 
some of the ideas are not held more closely, because this is an ideal arena 
for ISPs to have proprietary solutions that are better than their competitors.

[1] Jamshid Mahdavi, Sally Floyd, "TCP-Friendly Unicast Rate-Based Flow 
Control" http://www.psc.edu/networking/papers/tcp_friendly.html, January, 
1997.

Thanks for the feedback!
--MM--
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Matt Mathis     http://staff.psc.edu/mathis
Work:412.268.3319    Home/Cell:412.654.7529
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Evil is defined by mortals who think they know
"The Truth" and use force to apply it to others.