[99119] in North American Network Operators' Group
Re: Congestion control train-wreck workshop at Stanford: Call for Demos
daemon@ATHENA.MIT.EDU (Stephen Stuart)
Thu Sep 6 10:33:21 2007
To: Sean Donelan <sean@donelan.com>
cc: nanog <nanog@merit.edu>
In-reply-to: Your message of "Wed, 05 Sep 2007 13:36:21 -0400."
<Pine.GSO.4.64.0709051322480.254@clifden.donelan.com>
Date: Thu, 06 Sep 2007 14:32:07 +0000
From: Stephen Stuart <stuart@tech.org>
Errors-To: owner-nanog@merit.edu
> On Wed, 5 Sep 2007, Stephen Stuart wrote:
> >
> > [...]
>
> If there is no congestion, then this conversation serves no purpose.
> I'd like one infinite improbability drive too.
Sure. When mine arrives, I'll drop it into my matter replicator so you
can have one. :-)
> > Let's say our example student is capable of generating 95% of flows by
> > virtue of having access to 95% of the IP endpoints in the example
> > network. How do you envision the OS notion of "user" helping you
> > implement a per-user notion of fairness on the backbone?
>
> That's why I don't think operators care about "users" or "endpoints" but
> they do care about who is paying the bills. Operators care about the
> relative "fairness" between bill payers, not flows, sessions or users.
>
> Suppose MIT has a /8, Harvard as a /16; if MIT figured out they could get
> more backbone bandwidth than Harvard by multiplexing its "flows" across
> more addresses, and starving Havard students of backbone capacity.
> Suppose Harvard was paying for 50% of the backbone cost, while poor
> MIT could only afford to pay for 10% of the backbone cost.
>
> If the congestion point was always at the backbone edge, you might be
> able to accomplish this by making Harvard's connection bigger than MIT's
> connection. But lets imagine instead, during periods of little congestion
> you want both Harvard and MIT to use as much of the backbone as they can,
> and only when there is congestion do you want to "share" the backbone
> congestion "fairly" between them.
Yes, that's the notion that I was trying to convey.
I agree that operators don't care about users, my reason for steering
the conversation back toward them is that what kicked this sub-thread
off was the assertion that knowledge of user by the OS at a TCP
endpoint could somehow provide relevant information for resource
allocation in a network such that congestion is divided among
users. Techniques for trying to impose how congestion is "fairly"
shared among flows exist and aren't what we're talking about. Could a
technique be developed that used a notion of "user" in a network?
(From Fred's reply, I think that's what we're talking about.) I'd
argue that if it could it would be complex and therefore unsuitably
fragile in a service provider environment, and would lose all
relevance the moment a congestion point at an administrative boundary
was crossed.
Stephen
