Congestion control train-wreck workshop at Stanford: Call for Demos

Sean Donelan sean at
Wed Sep 5 15:01:36 UTC 2007

On Wed, 5 Sep 2007, Stephen Stuart wrote:
>> Operators always define the "user" as the person paying the bill.  One
>> bill, one user.
> It's easy to imagine a context where authentication at the application
> layer determines "user" in a bill-paying context. Passing that
> information into the OS, and having the OS try to schedule fairness
> based on competing applications' "guidance," seems like a level of
> complexity that adds little value over implementing fairness on a
> per-flow basis. In theory, any such notion of "user" is lost once the
> packet gets out on the wire - especially when user is determined by
> application-layer authentication, so I don't consider 802.1X or the
> like to be helpful in this instance.

Money and congestion are aggregated on many different levels.  At the dorm
level, money and congestion may be shared on a per-student basis while at
the institution level money and congestion may be shared on a 
per-department basis, and on a backbone level money and congestion may be
shared on a per-institution basis.

That's the issue with per-flow sharing, 10 institutions may be sharing a
cost equally but if one student in one department at one institution 
generates 95% of the flows should he be able to consume 95% of the 

>> Its fun to watch network engineers' heads explode.
> What if the person paying the bill isn't party to either side of the
> TCP session?

The person paying the bill is frequently not a party to either side of
individual TCP sessions, that is why you also frequently have disputes
over which TCP session should experience what level of congestion.

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