TELECOM Digest Editor noted in response to Lisa Hancock:
> [TELECOM Digest Editor's Note: I would think if it ever got that
> critical (where 'everyone' went with VOIP instead of landline) the
> VOIP administrators would develop the equivilent of the 'Erlang
> tables' in an effort to develop the amount of capacity needed to keep
> up with it. ....
> Telcos place their bets on the fact that at any typical time of
> day/day of week, _maybe_ one or two percent of their subscribers are
> actually using the phone. ...
> Why do you feel VOIP would be any different? I cannot imagine
> the _ratios_ would be much different than they are now.
Thanks for your comments. You are quite correct in the 'erlang'
calculations and that the system's capacity is based on a
small percentage of total subscribers.
My response was directed to the person who seemed to feel
that VOIP could easily replace POTS over much of the existing
network. I don't agree because I feel far more capacity will
be needed because:
1) While VOIP in itself isn't a resource hog (I presume), broadband is
still broadband and requires resources. They can't fit the same
number of broadband subscribers over the same lines as they can
traditional voice subscribers.
I suspect when a subscriber buys DSL, they are basically getting a
more "dedicated" line to the central office than what is given to a
POTS subscriber because they need a 'heavier' line to handle high
speed traffic than a voice grade line can support. So, just the very
use of broadband instead of POTS will require an increase of bandwidth
throughout the telephone system.
2) I think broadband will result in more usage. First off, there's
tremendous random hacking out there seeking unsecured terminals, so
while you're home terminal is supposedly sitting idle, it actually is
fending off (or participating in) hacking activity.
Secondly, since people won't have to bother dialing up and logging in
every time they have a quick question for the 'net, I suspect they'll
use it more often. Certainly the erlang concept of idle time will
still apply, but I expect they'll have to plan for more use. Kids are
hooked on this and today there are capacity issues as all the kids
come home from school and Instant Message or play games with each
3) Some of the infrastructure of the existing voice telephone system
isn't too well suited to high speed data transmission. Old drop lines
and neighborhood loops might suffer with crosstalk issues and
attenuation with high data speeds. Not all intermediate loop-to-CO
lines multiplexors are modern.
4) Another problem is rapid obsolescence. Telephone gear is expensive
and intended for a long lifespan. Yes today's gear is "programmable"
but perhaps an ESS installed ten years ago might not have the hardware
to support what is desired today. Likewise for older fibre systems.