[e2e] opening multiple TCP connections getting popular
rbriscoe at jungle.bt.co.uk
Sat Sep 1 02:02:37 PDT 2007
I composed responses yesterday to each of your points, but I've realised
there's no purpose in sending them until the underlying terms of reference
At 08:00 31/08/2007, Joe Touch wrote:
>Bob (et al),
> >> (and, as others have noted, it's not
> >> clear we _need_ to do anything).
> > Tell that to the CEO of any network operator. I think you're saying
> > there's not an engineering problem. But that's because resource
> > allocation problems are economic problems not engineering problems...
>No - I'm saying it isn't a problem. Whether it's economic or otherwise,
>as others have noted, not being 'fair' depends on an agreed concept of
>fairness. We have one now - per-TCP connection, relative to RTT. That's
>not perfect, but it is a definition, and it does work.
Well, most people who have entered this debate (mosly on tsvwg) have tried
to distance themselves from ever having been definite about per-TCP
connection/RTT as the agreed measure.
Of course there's not a problem... if you're measuring it the way you
are... but that's because the measure you're using isn't a relevant measure
- fairness is a social science issue so you need a social or economic
measure. Otherwise your judgement of whether 'it works' is circular...
Imagine a country had a tax system based on the number of transactions
entering and leaving a person's bank accounts.
* I'm saying such a metric doesn't produce a fair taxation system (e.g.
high earners stuff more money through less transactions).
* By analogy, by sticking with transaction count as a measure, you're led
to argue that there's not a problem. You can cite surveys of the
transaction count into people's bank accounts that show people are being
taxed in fair proportion to this count, and further, you're led to say that
there can't be a problem because the spread of the count of transactions
between most and least is pretty small.
If you look instead at the different volumes of congestion that users cause
against how much each is contributing to the system, you should be able to
see there is a huge problem. There's also a far greater spread of
congestion volume caused by different users than is warranted by any value
they get from causing it - many orders of magnitude between the lowest
quartile and the highest, but the spread of contributions is probably
within an order of magnitude.
It's not just flow rate. Flow rate must be weighted by the prevailing
congestion at each instant and the result accumulated over /time/. Then
attributed to each /economic entity/. That's congestion volume per 'user'.
And, if we go straight to congestion volume without passing through flow
rate, the resulting accountability system is really simple.
Bob Briscoe, <bob.briscoe at bt.com> Networks Research Centre, BT Research
B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK. +44 1473 645196
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