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

[Rob Lith]

Greg

On 7 Jan 2009, at 15:45, Gregory Boehnlein wrote:

>> I would like to add some information about the capacity of the USB  
>> 2.0
>> connection. The USB 2.0 interface provides a theoretical speed of
>> 480,000,000 bits per second. A typical uncompressed phone  
>> conversation
>> uses about 64,000 bits per second per direction, plus some  
>> overhead; in
>> total less than 200,000 bits per second per phone call is used.  
>> Thus, the
>> theoretical concurrent number of conversations that the USB 2.0
>> interface can handle is 480,000,000 divided by 200,000: roughly 2,400
> calls for a
>> single USB 2.0 port. For more info, see
>> http://www.xorcom.com/astribank-technology/usb2-interface.html
>
> 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.

-----
Setting:
dtmf_detection=yes
echocancel=64

Results:
maximum load =  157 concurrent calls.

----
Settings:
dtmf_detection=yes
echocancel=32

Results:
maximum load  = 240 concurrent calls

Regards
Rob

>> Bottom line...the USB connection is not the bottleneck.
>
> From a bandwidth perspective, yes.. but what about 8 devices  
> interrupting on
> the bus at the same time? What does that do to latency and jitter?
>
>> Finding a PC with the required number of PCI slots would be a  
>> problem with
> the suggested
>> Sangoma solution.
>
> How hard is it to find a piece of server hardware w/ two PCI-E  
> slots? If you
> are going to be running 200+ channels, you better be running a decent
> enterprise piece of hardware...
>
>> As for the channel banks, since the 1U Astribank supports 32 channels
>> (as opposed to the typical 2U 24 channels supported by other  
>> types), the
>> Astribank is obviously the better choice.
>
> From a real-estate perspective, yes. It would be much better to have  
> 8 1u
> boxes connected to a pair of 2u servers. I agree it makes the wiring  
> job a
> lot less complicated. I've just never actually heard of anyone doing  
> this in
> production.
>
>> For a point-by-point comparison, see
>> http://www.xorcom.com/astribank-technology/astribank-vs-channel-banks.html
>
> This discusses nothing about latency or jitter when using 8 devices  
> on the
> same USB bus. Other than that, it looks like a nice comparison, and  
> there
> are certainly some perceived advantages.
>
>> I'd be happy to answer any other questions about this technology...
>
> OK..
>
> 1. Do you have anyone in the field that I can talk to that is  
> running 8
> Astribank 32 port units on a single Asterisk server?
>
> 2. How do you deal with latency / jitter issues when you have 8  
> devices
> interrupting on the USB bus?
>
>
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