[e2e] critical mass and access rate for www / ftp servers

[Finkenzeller Michael]

Hi e2e and P2Prg list,

sorry for cross-posting but I think this is relevant to both lists.

We want to estimate the critical mass of an e2e distributed network
monitoring service, similiar to M-Coop. Therefor we do some simulations with
a self-made simulation tool. With "critical mass" for a distributed
monitoring service I'm interested in "How much peers are necessary to get a
certain amount of accuracy for e.g. bandwidth monitoring or topology
discovery".

My question:
Are there any models for an "average" surfer, to estimate the rate of
requests to a set of www-servers or ftp-servers? Or to put in a different
way. How often per minute is a different web/ftp server accessed by the an
"average" user. I know "average" is always an over-simplification. More
detailed models / approaches are also welcome :-)
Maybe this can be concluded by analyzing a representative number of
web-caches / proxys.

I would also be happy on information about "critical mass" of P2P services
in general. 

Thanks for your assistance,
Michael