[e2e] Congestion control as a hot topic in IETF

Detlef Bosau detlef.bosau at web.de
Fri Mar 8 07:33:18 PST 2013

Am 08.03.2013 15:00, schrieb Jon Crowcroft:
> congestion/contention
> involve multiple senders competing for a resource,
> and partitioning the use of that resource
> when you have multiple packets in flight (sure, intercontinental fiber a bit, and ong haul radio links more) then
> sure but the origins of the scheme are shared resource in the sense of the output link at the
> the bottleneck as measured by a queue building in the buffer just behind that
> the media type of the link up to that point is irrelevant. the capacity is

As I said above: For VJCC, it simply doesn't matter, /where/ any packet 
in flight resides, the packet is in flight and that's it.

> btw, path loss is very real (and not at the antennae)


Or can you tell me where the waves have gone? Where the energy has gone? 
Data corruption is a phenomenon which occurs at the receiver. The 
problem is that the receiver cannot successfully rebuild a packet from 
what he received. The air interface has no idea of which waves are 
travelling along and whether they make any sense at all.

> - in freespace, with omnidorectional antennae its
> a feature of inverse square law of spreading the signal over a speherical surface ...plus
> there's atenuuation from signal energy being absorped (e.g. by water vapour or concrete) - etc etc

that are wonderful formulae for the received power. They don't tell you 
whether a packet will be successfully read. And that's why I said 
formulae, which describe a "bandwidth" depending on the distance 
base-station/mobile, I referred to "Modelling Computer Networks for 
Emulation" by Rothermel, Herrscher, Leonhardi from 2002, are pleasant to 
read, however the model is completely nonsense.

And I wonder, why no communication engineer and no signalling theorist 
has made objections here so far, sometimes I think these guys simply 
ignore us CS guys because we would continue telling nonsense here and no 
one wants to spend his time in useless arguments. I thin, CE and EE guys 
simply don't take us seriously.

> your mixing it up with interference with concurrent senders o nthe receive antennae (which is fixable using mimo and
> smart processing - viz
> http://conferences.sigcomm.org/sigcomm/2012/paper/sigcomm/p235.pdf

I don't think so. In that paper, one discusses and uses an "effictive 
SNR algorithm", is this correct?

And where can you derive a throughput from the SNR? Do you mix up signal 
power and data rate? If so, you simply misunderstood the Shannon-Hartley 

You may wonder why I get a bit upset here. However, a whole research 
project of mine yielded no results and it took years to understand, that 
people simply pulled my leg here. I wasted 4 years of my life for this 
research completely and years afterwards for indirect consequences.

So, please let's spare discussions on elementary signalling theory.

Detlef Bosau
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detlef.bosau at web.de                     http://www.detlef-bosau.de

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