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

Stephen Stuart stuart at
Wed Sep 5 11:54:27 UTC 2007

> On Tue, 4 Sep 2007, Stephen Stuart wrote:
> >>> Operators are probably more interested in the "fairness" part of
> >>> "congestion" than the "efficiency" part of "congestion."
> >>
> >> TCP's idea of fairness is a bit weird. Shouldn't it be per-user, not
> >> per-flow?
> >
> > How would you define "user" in that context?
> 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.

> 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?


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