dialogic was RE: [Asterisk-Users] "Glare" condition - How well does asteriskhandle?

[Scott Stingel]

Hi Steve-

Just briefly:

I was mentioning the old days to illustrate what an even low clock rate DSP
can do.  More recently (2000-2001), using D/600's we were able to drive a
large number of channels (8-12 E1's) for IVR.

All I'm trying to do is to illustrate both the beauty and the limitations of
taking the processor horsepower off the line interface card and doing
everything in the central processor.  The Digium boards are MUCH less
expensive than the Dialogic boards (about 15% the cost, if that, per
channel), but are not a plug-in replacement.  I've hit a real-world limit,
in my less-common environment, of about 4 E1's per chassis.  I believe this
limitation is not so much in the bit-rate i/o, but the PRI call setup
overhead.  I have communicated with a number of other asterisk developers
who have experienced this limitation, again in a high-volume IVR
environment.   I have demonstrated it to Mark as well...

To get back to the original subject a bit, Dialogic developed an elegant API
called Global Call, which maybe we can use, or at least learn something
from.

I'll let you have the last word if you like, Steve.... <s>

Cheers
Scott


Scott M. Stingel
President,
Emerging Voice Technology, Inc.
Palo Alto California & London England
www.evtmedia.com 

-----Original Message-----
From: asterisk-users-admin at lists.digium.com
[mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Steve Underwood
Sent: Thursday, May 27, 2004 10:05 AM
To: asterisk-users at lists.digium.com
Subject: Re: dialogic was RE: [Asterisk-Users] "Glare" condition - How well
does asteriskhandle?

Hi Scott,

Dialogic need a bit more than 1 50MHz 56001 per E1, as they do a modest echo
canceller, and have a few bells and whistles in their tone detector. They
don't have an awful lot, though. There is no reasonable codec they could
implement, for example. A modest 2.4GHz Pentium is at least 50 times as fast
as the 56001, if you do all the DSP in floating point (a Pentium tends to
suck doing integer DSP).

Lets see. Early 90s would be ISA cards in an industrial PC chassis full of
ISA slots. Heavy IVR means talking most of the time. 3k bytes/s per voice
for the commonest 24K ADPCM mode most people use with Dialogic. 
So, 12 E1s is 360 channels. 3kbytes x 360 = more than the ISA bus can
handle, before I even add up the disk loading. Does not compute.

On the other hand, how come you can only do 2 E1s of IVR with *? Lets take a
modest single 2.4GHz Pentium. It can easily handle a lot of channels of
voice playback. This is mostly disk limited, and even the slowest disk is
much faster than the fastest in the early 90s. The DTMF detector takes
almost nothing. You must be loading things up a lot with complex database
and other activities you would never have dreamed of loading your old
Dialogic machines with. The IVR part itself shouldn't be heavily loaded at
just 60 channels.

Regards,
Steve


Scott Stingel wrote:

>Hi Steve-
>
>Not to belabor this, but the PCI version of the Dialogic DMV600 board 
>has TEN 56311 DSP's per board - that's to handle only two E1's.  Having 
>programmed the Motorola 56000 series DSP's in my past life, I can 
>assure you that that's a fair bit of processing power.  In the "old 
>days" (early 90's) with our own designs, we were able to do all the 
>DTMF, as well as tone and voice detect for a 30-channel span with only one
50MHz 56001 DSP.
>
>http://www.intel.com/network/csp/products/7603ts.htm
>
>But real-world experience is more important.  The Digium TE4XXP boards 
>can barely handle 4 E1's in one high-powered chassis (again, high 
>volume IVR) - we used to routinely put 8-12 Dialogic-driven E1's in a 
>single 300 MHz chassis with not a burp.  The signalling, protocol, call 
>progress analysis etc are largely handled right on the Dialogic board.
>
>Anyway, sorry to run on about this..  I'm not knocking the Digium boards,
in
>fact I support them exclusively now for new customers.   But to have the
>support of Dialogic boards available for people who want to build 
>really large systems (or who have a ton of used Dialogics on hand) would be
nice.
>
>Regards
>Scott Stingel
>
>
>Scott M. Stingel
>President,
>Emerging Voice Technology, Inc.
>Palo Alto California & London England
>www.evtmedia.com
>
>
>-----Original Message-----
>From: asterisk-users-admin at lists.digium.com
>[mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Steve 
>Underwood
>Sent: Thursday, May 27, 2004 7:48 AM
>To: asterisk-users at lists.digium.com
>Subject: Re: dialogic was RE: [Asterisk-Users] "Glare" condition - How 
>well does asteriskhandle?
>
>Scott Stingel wrote:
>
>  
>
>>Not to mention that the Digium T1/E1 cards are about 1/5 the cost of 
>>Dialogic's.  That said, it should be noted that the Dialogic cards 
>>allow scaling to a much larger size within one chassis, thanks to 
>>heavy DSP horsepower helping out with the low level chores.
>> 
>>
>>    
>>
>The Dialogic cards don't have heavy DSP horsepower. They have rather 
>feeble DSP power. That is why they only do the simplest of tasks with 
>the onboard DSP.
>
>Regards,
>Steve
>  
>

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