[Nanog] Lies, Damned Lies, and Statistics [Was: Re: ATT VP: Internet to hit capacity by 2010]

michael.dillon at bt.com michael.dillon at bt.com
Wed Apr 23 22:40:11 UTC 2008

> However, as your chunk scheduling becomes more effective, it 
> usually becomes more expensive. At some point, its increasing 
> complexity will reverse the trend and start slowing down 
> copies, as real-world clients begin to block making chunk 
> requests waiting for CPU to make scheduling decisions.

This is not a bad thing. The intent is to optimize the whole
system, not provide the fastest copies. Those who promote QoS
often talk of some kind of scavenger level of service that
sweeps up any available bandwidth after all the important users
have gotten their fill. I see this type of P2P system in a similar
light, i.e. it allows the ISP to allow as much bandwidth use
as is economically feasible and block the rest. Since the end 
user ultimately relies on an ISP having a stable network that
functions in the long term (not drives the ISP to bankruptcy)
this seems to be a reasonable tradeoff.

> As seems to be a trend, Michael appears to be fixated on a 
> specific implementation, and may end up driving many 
> observers into thinking this idea is annoying :)  However, 
> there is a mathematical basis for including topology (and 
> other nontraditional) information in scheduling decisions.

There is also precedent for this in manufacturing scheduling
where you optimize your total systems by identifying the prime
bottleneck and carefully managing that single point in the 
chain of operations. I'm not hung up on a specific implementation,
just trying to present a concrete example that could be a starting
point. And until today, I knew nothing about the P4P effort which
seems to be working in the same direction.

--Michael Dillon

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