North American Network Operators Group

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

  • From: Iljitsch van Beijnum
  • Date: Fri Oct 26 03:41:48 2007

On 25-okt-2007, at 18:50, Sean Donelan wrote:

Comcast's network is QOS DSCP enabled, as are many other large provider networks. Enterprise customers use QOS DSCP all the time. However, the net neutrality battles last year made it politically impossible for providers to say they use QOS in their consumer networks.

And generating packets with false address information is more acceptable? I don't buy it.

The problem is that ISPs work under the assumption that users only use a certain percentage of their available bandwidth, while (some) users work under the assumption that they get to use all their available bandwidth 24/7 if they choose to do so. Obviously the two are fundamentally incompatible, which becomes apparent if the number of high usage users starts to fill up available capacity to the detriment of other users.

I don't see any way around instituting some kind of traffic limit. Obviously that can't be a peak bandwidth limit because that way ISPs would have to go back to selling 56k connections. (Still enough to generate 15 GB or so per month in one direction.) So it has to be a traffic limit. But then what happens when a customer goes over the limit? I think in the mobile broadband business such customers are harassed to leave. That's a good business practice if you can get away with it, but the Verizon case shows that you probably can't in the long run. So after a customer goes over the traffic limit, you still need to give them SOME service but it must be a reduced one for some time so the customer doesn't keep using up more than their share of available bandwidth. One approach is to limt bandwidth. The other is dumping that user in a lower traffic class. If there is a reasonable amount of bandwidth available for that traffic class, then the user still gets to burst (a little) so this gives them a better service level. I don't see how this logic violates net neutrality principles.

Until P2P applications figure out how to play nicely with non-P2P network uses, its going to be a network wreck.

And how exactly do you propose that they do that?

My answer is: set a different DSCP. As I said before, at least one popular BitTorrent client can already do that. And if ISPs like Comcast already have diffserv-enabled networks, this seems like a no- brainer to me. Don't forget that the first victim of an overloaded last mile link is the user of that link themselves: if they let their torrents rip at max speed, they get in the way of their own interactive traffic.