[Iccrg] review of open-research draft

[Lachlan Andrew]

Greetings Wes,

2008/9/19 Eddy, Wesley M. (GRC-RCN0)[VZ] <Wesley.M.Eddy at nasa.gov>:
> I've reviewed the open-research draft:
> http://tools.ietf.org/html/draft-irtf-iccrg-welzl-congestion-control-ope
> n-research-02
>
> - Section 2.3, final paragraph: It seems to me that if an architecture
> is
>  built to support cost-fairness that equal-costs result in flow-rate
>  fairness as a degenerate case; that is, flow-rate fairness is a
> special
>  case of cost-fairness.  One can be used to build the other, but not
>  vice-versa.

I think that over-simplifies the problem.  In a general network, cost
accumulates along a path (a two-hop flow will have the sum of the
costs of the two links) while flow rate doesn't.

I'm not exactly sure what you mean by "equal cost", but I'm guessing
that you mean that all flows have equal utility functions.  If that is
the case, then we certainly don't get equal rate in multi-bottleneck
networks.

My own comment on that paragraph would be that deciding between
rate-fairness and cost-fairness *does* need more research.  I'm not
convinced that either is understood well enough for "assessing how bad
fairness problems could become if they are not addressed rigorously".
However, I agree that more research won't necessarily convince either
side to change their opinions, and that debate is needed for that.

Cheers,
Lachlan

-- 
Lachlan Andrew Dept of Computer Science, Caltech
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