[Iccrg] RE: Iccrg Digest, Vol 4, Issue 10

[Dado Colussi]

Fil Dickinson wrote:
> 'Network congestion is a state where there are insufficient resources in a network for a flow that result in excessive delay. This in turn results in the flow failing to meet minimum effective performance.'


If we consider Keshav's utilities mathematically, we probably see 
functions u: X -> Y where X is a set of resource bundles and Y is some 
set with order property. Keshav says that a source experiences 
congestion if u(x1) > u(x2) where x1 and x2 are user's resource bundles 
before and after an increase in network load. I find this definition 
quite elegant and expressive.

The insufficient resources you suggest are all those resource bundles 
that don't result in maximum utility when the utility is sensitive to 
excessive delay (or throughput, as in your second definiton). However, 
utility functions differ per application and even per user basis and are 
not limited to excessive delay only (or throughput only). Furthermore, 
the Internet exists for its users and it's more important to adjust it 
for the users than for mere existence. That's why I think a user-centric 
approach is well justified.

You're right about the problem of measurement. I think it would be 
essential to discuss u, X and Y. If we knew them, u and X in particular, 
we would be in a better position to decide what tradeoffs to make in 
suggesting a framework for measurement. It's not feasible to find 
utility functions for each application and user but I do think it would 
be feasible to find a sufficiently expressive classification that would 
enable us to justify the tradeoffs. I'm not suggesting it would be easy 
though.


Dado