[asterisk-biz] ATA Bank for Asterisk, 400 phones

[Gregory Boehnlein]

> > Have you done this in production? Is there an actual case study
> and/or
> > company that is doing this with the hardware that I can speak with?
> > I'd like
> > to see what performance is like with 256 active channels on a USB
> bus.
> 
> Here are some practical test done by Xorcom. Depending mainly on the
> echo can tail you can get up to 240 calls with 32 taps, as the system
> has to work harder for 128 taps you only get 93...
>
> XR3000 + on board [2ports PRI] + [24FXS]
> 16 Astribanks [32FXS]
> System Total:  2 PRI, 536 extensions
> 
> Setting:
> dtmf_detection=yes
> echocancel=128
> 
> Results:
> maximum load  = 93 concurrent calls.

OK.. so this might work in a system where you have a 4:1 call ratio.. I.E.
where only 1 of every 4 channels is in use at the same time.

This would lend itself very well to a Hotel or other "casual use" sort of
deployment.

What about in a call-center or high-volume PBX situation where you are
running at 1:1 ratios?

Also, keep in mind that a PRI based card is most likely going to have
hardware echo cancelling (Octasic based) PRI based Echo Canceller that can
do 128 tap echo cancellation on all channels at simultaneously.

If you use E-1 signalling between the Channel Banks and the Asterisk box,
you'll get 30 channels of usable audio (8 x 30 = 240). If you double up the
Sangoma cards, you can have 16 PRI (480 channels) into a single box. And
yes, I do know and have seen some people running 16 and 24 PRIs into an
Asterisk server in the field.

Personally, I'd rather diversify this sort of load over multiple boxes.. say
using Digium TE412P cards + Hardware Transcoding cards.
 
> -----
> Setting:
> dtmf_detection=yes
> echocancel=64
> 
> Results:
> maximum load =  157 concurrent calls.
> 
> ----
> Settings:
> dtmf_detection=yes
> echocancel=32
> 
> Results:
> maximum load  = 240 concurrent calls

Where is the Echo Cancellation done? At the Astribank on Hardware DSP? Or at
the Asterisk server using software echo cancellers?

Personally, I've switched to using all hardware based echo cancelling.. it
"just works" and it has addressed every echo concern that I've ever run into
w/ Asterisk. I can't imagine goine back to software echo cancelling ever
again.