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New Member

users per PRI

we are moving our NOC and i need to figure out how many users we should allow per PRI.

we have 400 users so i need to figure out how many PRI's we'll need. I think i remember reading 5 users per one phone line.

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Accepted Solutions
Hall of Fame Super Red

Re: users per PRI

Hi Jerry,

Just wanted to add a note to Sankar and Paolo's good onfo here. The old telco rule is called the "1 in 10" Trunking rule. 1 Trunk/Channel per 10 users. Given the fact that a NOC would probably have a much higher usage rate than your average business your "1 in 5" thought might be perfect. You can always engage your service provider to do a Traffic Study that will also include busyhour averages in your current setup. It is probably good to be over-trunked rather than under-trunked, especially with an environment like yours :)

Hope this helps!

Rob

8 REPLIES
Hall of Fame Super Gold

Re: users per PRI

Sorry if that seems obvious, but what is the usage now?

New Member

Re: users per PRI

im not sure how to monitor the PRI. i run solar winds for the ppp t-1's.

Hall of Fame Super Gold

Re: users per PRI

Telnet to the router during a peak hour. Do "show isdn status" and note the number of used channels.

Re: users per PRI

Use Erlangb calculator for trunk sizing

http://www.erlang.com/calculator/erlb/

Hall of Fame Super Red

Re: users per PRI

Hi Jerry,

Just wanted to add a note to Sankar and Paolo's good onfo here. The old telco rule is called the "1 in 10" Trunking rule. 1 Trunk/Channel per 10 users. Given the fact that a NOC would probably have a much higher usage rate than your average business your "1 in 5" thought might be perfect. You can always engage your service provider to do a Traffic Study that will also include busyhour averages in your current setup. It is probably good to be over-trunked rather than under-trunked, especially with an environment like yours :)

Hope this helps!

Rob

Re: users per PRI

I agree with Rob. I usually do a 1-10 ratio on PRIs. Even that sometimes is a little much, but id rather be over than under if you can. CDR systems will help you alot, the local telco will probably never help you on your traffic patterns, no matter how much you ask, and they use 1-4 ratio (so they can sell more PRIs to you!)

If it's a call center, it's almost a 1-1 ratio with extra for admin personel, etc.

cheers!

New Member

Re: users per PRI

thanks everyone - i'll get on it.

speaking of these PRI's there down - a fun morning at work.

New Member

Re: users per PRI

hey

the real time monitoring tool tells you whats in use...

Very useful tool

Cheers

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