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Re: Can P2P applications learn to play fair on networks?

  • From: Marshall Eubanks
  • Date: Thu Oct 25 17:45:00 2007


On Oct 25, 2007, at 1:09 PM, Sean Donelan wrote:


On Thu, 25 Oct 2007, Marshall Eubanks wrote:
I have raised this issue with P2P promoters, and they all feel that the
limit will be about at the limit of what people can watch (i.e., full
rate video for whatever duration they want to watch such, at somewhere between 1
and 10 Mbps). From that regard, it's not too different from the limit _without_ P2P, which
is, after all, a transport mechanism, not a promotional one.

Wrong direction.

In the downstream the limit is how much they watch. The limit on how much they upload is how much everyone else in the world wants.

With today's bottlenecks, the upstream utilization can easily be 3-10 times greater than the downstream. And that's with massively asymetric upstreams capacity limits.

When you increase the upstream bandwith, it doesn't change the downstream demand. But the upstream demand continues to increase to
consume the increased capacity. However big you make the upstream, the world-wide demand is always greater.

I don't follow this, on a statistical average. This is P2P, right ? So if I send you a piece
of a file this will go out my door once, and in your door once, after a certain (& finite !) number of hops
(i.e., transmissions to and from other peers).

So if usage is limited to each customer, isn't upstream and downstream
demand also going to be limited, roughly to
no more than the usage times the number of hops ? This may be large, but it won't be unlimited.

Regards
Marshall


  And that demand doesn't seem
to be constrained by anything a human might watch, read, listen, etc.

And despite the belief P2P is "local," very little of the traffic is local particularly in the upstream direction.


But again, its not an issue with any particular protocol. Its how does
a network manage any and all unbehaved protocols so all the users of the
network, not just the few using one particular protocol, receive a fair share of the network resources?

If 5% of the P2P users only used 5% of the network resources, I doubt
any network engineer would care.