North American Network Operators Group

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

  • From: Mikael Abrahamsson
  • Date: Mon Oct 22 02:15:16 2007

On Sun, 21 Oct 2007, Eric Spaeth wrote:

They have. Enter DOCSIS 3.0. The problem is that the benefits of DOCSIS 3.0 will only come after they've allocated more frequency space, upgraded their CMTS hardware, upgraded their HFC node hardware where necessary, and replaced subscriber modems with DOCSIS 3.0 capable versions. On an optimistic timeline that's at least 18-24 months before things are going to be better; the problem is things are broken _today_.

Could someone who knows DOCSIS 3.0 (perhaps these are general DOCSIS questions) enlighten me (and others?) by responding to a few things I have been thinking about.

Let's say cable provider is worried about aggregate upstream capacity for each HFC node that might have a few hundred users. Do the modems support schemes such as "everybody is guaranteed 128 kilobit/s, if there is anything to spare, people can use it but it's marked differently in IP PRECEDENCE and treated accordingly to the HFC node", and then carry it into the IP aggregation layer, where packets could also be treated differently depending on IP PREC.

This is in my mind a much better scheme (guarantee subscribers a certain percentage of their total upstream capacity, mark their packets differently if they burst above this), as this is general and not protocol specific. It could of course also differentiate on packet sizes and a lot of other factors. Bad part is that it gives the user an incentive to "hack" their CPE to allow them to send higher speed with high priority traffic, thus hurting their neighbors.

Mikael Abrahamsson    email: [email protected]