[100314] in North American Network Operators' Group
Re: Can P2P applications learn to play fair on networks?
daemon@ATHENA.MIT.EDU (Eric Spaeth)
Sun Oct 21 16:58:29 2007
Date: Sun, 21 Oct 2007 15:56:08 -0500
From: Eric Spaeth <eric@spaethco.com>
Reply-To: eric@spaethco.com
To: nanog@merit.edu
In-Reply-To: <471BA90E.9030206@eeph.com>
X-SpaethCo-MailScanner-From: eric@spaethco.com
Errors-To: owner-nanog@merit.edu
Matthew Kaufman wrote:
> Maybe Comcast should fix their broken network architecture if 10 users
> sending their own data using TCP (or something else with TCP-like
> congestion control) can break the 490 other people on a node.
>
That's somewhat like saying you should fix your debt problem by
acquiring more money. Clearly there are things that need to be improved
in broadband networks as a whole, but the path to that solution isn't
nearly as simple as you make it sound.
> Or get on their vendor to fix it, if they can't.
>
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_.
> If that means traffic shaping at the CPE or very near the customer,
> then perhaps that's what it means, but installing a 3rd-party box that
> sniffs away and then sends forged RSTs in order to live up to its
> advertised claims is clearly at the "wrong" end of the spectrum of
> possible solutions.
>
On a philosophical level I would agree with you, but we also live in a
world of compromise. Sure, Comcast could drop their upstream sync rate
to 64kbps, but why should they punish everyone on the node for the
actions of a few? From the perspective of practical network
engineering, as long as impact can be contained to just seeding
activities from P2P applications I don't think injected resets are as
evil as people make them out to be. You don't see people getting up in
arms about spoofed TCP ACKs that satellite internet providers use to
overcome high latency effects on TCP transfer rates. In both cases the
ISP is generating traffic on your behalf, the only difference is the
outcome. In Comcast's case I believe for their solutions the net
effect is the same; by limiting the number of seeding connections they
are essentially rate limiting P2P traffic. It just happens that reset
inject is by far the easiest option to implement.
> Maybe Comcast's behavior will cause all 500 neighbors to find an ISP
> that isn't broken. We can only hope.
Broken is a relative term. If Comcast's behavior causes their heavy P2P
users to find another ISP then those who remain will not have broken
service. For $40/mo you can't expect the service to be all things to
all people, and given the shared nature of the service I find little
moral disagreement with a utilitarian approach to network management.
-Eric
