[e2e] [SPAM] opening multiple TCP connections getting popular

Detlef Bosau detlef.bosau at web.de
Thu Aug 30 07:27:06 PDT 2007

Michael Welzl wrote:
> That raises an interesting question: given the fact that different
> experimental high-speed TCP variants are already widely deployed,
> and given the fact that the Window Scaling option is not widely
> used (*), what would happen to the net in the scenario that you
> sketched of Japan, where fibre to the home is becoming more common,
> if people would start using the Window Scaling option?

That depend´s on the scenario.

Once, I was told that ba a colleague, that  enabling Window Saling 
drastically enhanced his throughput from somewhere in USA to Germany. 
Interestingly, as it turned out, he used some quite ordinary 600 MBps 
line as backbone.

Now, I think, what´s happened is quite easy to understand.

First: Perhaps, this was probably the first time when the DRAM of the 
installed c*sc* hardware along the path was fully used if not exhausted. 
To my knowledge, this is called "protection of investment".

Second: Any competing users will have loved him for that one, because 
_he_ _certainly_ achieved high throughput.

Basically, TCP congestion control is heterachical without any central, 
hierachical control
So, there are almost necessarily some more or less sophisticated 
scenarios where TCP congestion control is not that fair than a 
hierachical, central admission control.

You are of course always free to define concrete requirements, if 
necessary, which can be so implemented then using ressource control and 
admission control mechanisms. However, this will require more or less 
complex router support and does not fit exactly into the "orthodox" end 
to end paradigm, where the "intelligence" of a TCP flow is situated in 
the end points and not in the intermediate nodes.

This is however neither a brand new insight in TCP nor does it cause 
unbearable grief in all days life.


Detlef Bosau                          Mail:  detlef.bosau at web.de
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