asterisk users - Sep 2004 - Questions about PRI lines for modem banks and Asterisk

I have a friend with a PRI coming into a modem bank that is receiving 
56K modem calls and some ISDN data calls.  He wants to dump his analog 
office phone lines and use some of the capacity on the PRI. I have been 
digging through the mail archives and Wiki site on this subject but the 
information I found doesn't give me a high enough confidence to go buy a 
few T1 cards and try it out.  There is talk of using Asterisk as the 
termination of the PRI from the PSTN and then forward calls for the 
modem bank via another T1 span and a cross-over cable.  Others talk of 
splitting the calls off with specialized equipment before it reaches the 
Asterisk box.  Does anyone actually have the same (or similar) scenario 
and if so what was your solution?  If you are using Asterisk to do the 
switching, I would be interested in seeing your relevant config files.  
My primary concerns are:
- The load on the Asterisk box if it is acting as a router for the 
incoming ISDN calls.
- Effect of 56K modem dialup connections or ISDN data calls passing 
through an Asterisk box.

Any success stories would be appreciated.

On Sat, 2004-09-11 at 15:40, Clif Jones wrote:
> I have a friend with a PRI coming into a modem bank that is receiving 
> 56K modem calls and some ISDN data calls.  He wants to dump his analog 
> office phone lines and use some of the capacity on the PRI. I have been 
> digging through the mail archives and Wiki site on this subject but the 
> information I found doesn't give me a high enough confidence to go buy
a
> few T1 cards and try it out.  There is talk of using Asterisk as the 
> termination of the PRI from the PSTN and then forward calls for the 
> modem bank via another T1 span and a cross-over cable.  Others talk of 
> splitting the calls off with specialized equipment before it reaches the 
> Asterisk box.  Does anyone actually have the same (or similar) scenario 
> and if so what was your solution?  If you are using Asterisk to do the 
> switching, I would be interested in seeing your relevant config files.  
> My primary concerns are:
> - The load on the Asterisk box if it is acting as a router for the 
> incoming ISDN calls.
> - Effect of 56K modem dialup connections or ISDN data calls passing 
> through an Asterisk box.
Asterisk can handle your ISDN calls itself. So you really only need to
worry about passing the 56k calls through to the modem bank. Should
work, but I don't know if you can keep high 56k speed. 
-- 
Steven Critchfield <critch@basesys.com>

On Sat, 11 Sep 2004, Clif Jones wrote:
> I have a friend with a PRI coming into a modem bank that is receiving 
> 56K modem calls and some ISDN data calls.  He wants to dump his analog 
> office phone lines and use some of the capacity on the PRI. I have been 
> digging through the mail archives and Wiki site on this subject but the 
> information I found doesn't give me a high enough confidence to go buy
a
> few T1 cards and try it out.  There is talk of using Asterisk as the 
> termination of the PRI from the PSTN and then forward calls for the 
> modem bank via another T1 span and a cross-over cable.  Others talk of 
> splitting the calls off with specialized equipment before it reaches the 
> Asterisk box.  Does anyone actually have the same (or similar) scenario 
> and if so what was your solution?  If you are using Asterisk to do the 
> switching, I would be interested in seeing your relevant config files.  
> My primary concerns are:
> - The load on the Asterisk box if it is acting as a router for the 
> incoming ISDN calls.
> - Effect of 56K modem dialup connections or ISDN data calls passing 
> through an Asterisk box.
We have something like this set up. 
  pstn <-pri-> asterisk <-pri-> pbx <-bri-> isdn modems
                                    <-bri-> isdn modems
                                       ...

The isdn modems handle both isdn data and analog modem calls without 
problems. The call is bridged inside the TE405P card I think. There is no 
noticable load on the asterisk server.

Peter