[e2e] Congestion control as a hot topic in IETF

Detlef Bosau detlef.bosau at web.de
Tue Mar 5 08:40:17 PST 2013

Am 05.03.2013 13:07, schrieb Scharf, Michael (Michael):
>> Am 04.03.2013 23:07, schrieb Scharf, Michael (Michael):
>>> There has been some interesting research on whether a
>> transport protocol could work without any congestion control.
>> One reference is: B. Raghavan and A. Snoeren, "Decongestion
>> Control", ACM SIGCOMM Workshop on Hot Topics in Networks, 2006.
>> I remember that you, some years ago, asked whether networking
>> can be done without flow control.
> My comment is about network designs that typically assume erasure codes and flow-based queueing/scheduling in all network nodes. Actually, it took me a while to fully understand why this is no alternative to the way Internet congestion control works today. But, for what it is worth, I found the overall idea intesting.
> Michael

It's perhaps not the focus of this discussion, but you perhaps remember 
our private discussion years ago, where I started to make a difference 
between bandwidth and throughput, particularly as the "throughput delay 
product" is something completely different from the "bandwidth delay 
product". These are perhaps no central aspects of our discussion, 
however it somehow illustrates where some of the confusion may come from.

And I made quite some turnarounds myself during the last years. Starting 
from mobile networks, as you may remember, ending up in the insight that 
VJCC does not really work with a single mobile wireless link 
(!!!!!!!!!!!!!!!) and that this does not change if we put 30 wired links 
in advance of the mobile one and 50 other behind - and then argue that 
VJCC will work end to end.

No. Like in maths, one counterexample disproves a theorem.

However, different from math, VJCC is not a theorem but a mechanism 
based upon quite some, if implicit, assumptions. So it may well be, and 
actually is the case, that these assumptions do not hold in some network 
so VJCC is not applicable and may lead to unwanted results.

This is no way a disaster, it is some kind of collective learning.

Detlef Bosau
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