[e2e] Why do we need congestion control?

Detlef Bosau detlef.bosau at web.de
Wed Apr 3 08:43:37 PDT 2013

I've just had a first look at the Snoeren paper.


Remembers me of typical parliament debates.

Let the people babble as much as they can - afterwards make a "fair 
bullshit removal" (so, no party is advantaged while others are 
disadvantaged) and the rest is the reasonable content of the debate.

Perhaps, my knowledge is a bit outdated here, but I well remember times 
where people had to pay for network resources.

The idea is interesting anyway, however we should carefully discuss who 
eventually does the clean up work and which are the consequences of 
I agree with Dave, that erasure codes do not obviate the need for 
congestion control. Actually, at the moment we shift around the 
responsibilities, what does not necessarily clarify the situation.

The idea of the paper is appealing: When we have 10 flows, let each flow 
send as fast as he can - the network imposes fair drop on each flow and 
hence the experienced goodput is a consequence of the drop rate. A 
single flow may experience no drop and hence yields high good put, if 
the network is fully overcrowded, each flow experiences high packet drop 
and the goodput  is  hence low.

The first immediate objection is the same as with VJCC: How is fairness 
defined and what is the common resource for two flows? Particularly, we 
meet the same difficulty here as I have seen it in some papers by Frank 
Kelly: Implicitly, the common resource is always sending time.
What about wireless networks? Where the shared resource is not always 
time but power? And when I may elaborate on this one: In UMTS like 
networks, the approach would only lead to maximum interference in a cell 
- which most likely simply would render the cell unusable.

Detlef Bosau
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