[Asterisk-biz] Trunk-to-subscriber ratios

[Paul]

Justin B Newman wrote:

>
> I'll also note that if you have 1 line, you probably can't 
> oversubscribe it 8:1.  If you have 1 PRI, you may be able to.  If you 
> have 100 PRIs, the odds get better.

Circa 1992 from a friend with an answering service. It was something like:

Trunks = Clients/Ratio + Ratio

This was what he said was an absolute minimum for any business that 
oversubscribes lines - paging, dialup, voicemail, answering, etc.

He also said that the absolute minimum trunks for startup would be Ratio 
* 2 in most cases because of the way equipment is offered(like analog 
line cards typically coming in 4 or 8 line versions). Also in most cases 
Ratio * 2 would still be far short of the capacity needed when 
subscriptions reach the breakeven point.

So the minimum startup for 8:1 would be 16 trunks. I think my friend's 
formula makes sense. It helped me see how much capital I needed just for 
the equipment, NRC and a few months MRC in one case. Prevented me from 
getting in over my head.

Reduce the value of Ratio accordingly to deal with expected growth and 
the provisioning time needed for that.