[e2e] Congestion control as a hot topic in IETF

Detlef Bosau detlef.bosau at web.de
Mon Mar 18 16:39:48 PDT 2013

Am 09.03.2013 14:31, schrieb Fred Baker (fred):
> I'm personally of the opinion that loss-based congestion controls are 
> inefficient, for the simple reason that a mechanism that tunes to the 
> knee will generally achieve the same bit rate end to end as one that 
> tunes to the cliff (they will both, given that they have enough data 
> to do so, fill the bottleneck); However, one that tunes to the cliff 
> has to assume and account for some amount of self-inflicted loss, 
> which implies recovery delays and a reduction in end to end bit rate 
> comparable to the retransmission rate. CAIA CDG has, I think, 
> characteristics that would enable it to eliminate a number of data 
> center issues and issues on the wide wooly Internet. Yes, we need some 
> form of congestion control. We have proven that to ourselves time and 
> again. The question is "with what characteristics, seeking to achieve 
> what goal?" 

 From what you say it becomes clear, that "congestion control" pursues 
at least three goals.

1.: Stability (in the sense of "no congestion loss").
2.: Probing/Tuning (to the knee or to the cliff, that doesn't really 
matter here).
3.: Resource sharing / scheduling.

These goals are intertwined, while the first one is the easiest to 
accomplish: Simply obey the conservation principle and you're done.

The interesting issues are the second and the third one.

Particularly for the third one, I'm not quite sure whether we really 
focus on the correct resource here.

Detlef Bosau
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