Re: [Bloat] Bufferbloat Paper

[Michael Richardson <mcr@sandelman.ca>]

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(not having read the thread yet on purpose)

Reading the paper, my initial thought was: big queues can only happen
where there is a bottleneck, and on the 1Gb/s CCZ links, that's unlikely
to be the case.  Then I understood that he is measuring there because
(he can and) really he is measuring the delay to other peers, from a
place that can easily fill the various network queues.

I don't understand the analysis of RTT increases/decreases.

It seems to me, that for a given host pair, there is some RTT
theorectical minimum, which represents a completely empty network, and
perhaps one can observe something close to it in the samples, and maybe
a periodic ICMP ping would have been in order, particularly when the
host pair was not observed to have any traffic flowing.  

The question of queuing delay then can be answered by how much higher
the RTT is over some minimum.  (And only then, does one begin to ask
questions about GeoIP and speed of photons and speed of modulated
electron wavefronts).  
Maybe that's the point of the RTT increase/decrease discussion in
section 2.2

This paper seems to really be about increasing IW.
The conclusion that 7-20% of connections would even benefit from an
increase in IW, and that long lived connections would open their window
anyway, for me, removes the question of bufferbloat from the IW debate.

The conclusion that bloat is <100ms for 50% of samples, and <250ms
for 94% of samples is useful: as the network architect for an commercial
enterprise focused VoIP provider, those numbers are terrifying.  I think
the situation is worse, but even if it's as good as reported, we can not
afford an additional 250ms delay in the circuits :-) 

now, to read the thread.

-- 
]               Never tell me the odds!                 | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works        | network architect  [ 
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [ 
	










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