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

[Rob Lith]

On 7 Jan 2009, at 18:04, Gregory Boehnlein wrote:

>>> 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.

At the moment it is software - I agree hardware is 1st prise!

Regards
Rob