[ale] OT: Starting an ISP and analyzing capabilities...

[John Wells]

Guys,

I have a friend who owns a company that recently acquired a dedicated
OC-12 SONET. He's considering starting an ISP with this bandwidth (and
wishes to make it entirely linux based), and in passing
asked me how to determine the users this could support.

I've never attempted at calculating network load like this, so I
informed him that he'd be better off speaking with a network expert.

Either way, not knowing how to do this bothers me, and I'd still like to
provide him with a rough estimate.  How would you go
about calculating the total number of users this could support?  My
feable attempt was to get the total capacity (listed in a book of mine
as 594.43 Mbps user data), multiply by 1024 to get kbps, and then divide
by 56 (assuming everyone connected at once and was using the full
possible bandwidth allocated to them...56k).

This looks like:
594.43 * 1024 = 608696.32
608696.32 / 56 = 10869.58

This suggests that at any given time, the bandwidth could support 10,869
users connected (and max'ing their connections) at 56k.

I know this is way too simplistic, so I ask anyone with experience in
these matters to show me where I'm wrong and how to correctly derive the
estimates.

Also, in typical ISP operations I'm sure they don't allocate 56k per user
exclusively, rather it would seem they would allocate on demand, thereby
freeing the unused bandwidth when user activity drops off.  Is this
assumption correct?

Finally, are there any good books out there that cover this sort of
analysis?  What about any books out there that would describe how to set
up a modem bank and allow users to connect?

Thanks very much for your help.

John






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