That seams to be the same issue with SpanDSP. It seams that the high
interrupt rate is slipping. In the case of the SpanDSP issue it is drop
1 out of 50 packets. This is of course with the TDM cards (fxo/fxs) not
the Single or Quad span cards. I think it may be time to look at the Zap
vased code to see if buffering or interrupt queues of a sort may be
needed.
-----Original Message-----
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Matt Roth
Sent: Tuesday, April 26, 2005 12:58 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] Digium Quad Span Cards
Initially, I believed that the limitation was the PCI bus, but I was
mistaken. There is a lot of confusion surrounding this issue, and it
would be great if someone stepped forward with a concrete answer. That
said, here's what I've learned about the issue through my research.
We started off asking a Digium representative about putting 4 quad-span
cards in a single machine and got the following response:
- I'd use two machines, with two quad cards each. And then, I'd need to
be using only the G.711 ulaw protocol. Then, I'd still use a mid-range
dual Xeon CPU machine in the 2.4GHz+ spectrum.
David Mandelstam of the Asterisk Biz List provided me with this
explanation:
- Zaptel drivers produce at least one interrupt per millisecond per
board, which is minimal if the interrupt handlers are short. But on a
heavily loaded machine doing lots of echo cancellation, each interrupt
can approach 1 millisecond in length. So if there are interrupts coming
from several cards, you can see how you could get into trouble.
So it looks like processor interrupts are the culprit.
Possible solutions to this problem include (please feel free to add to
this list):
- An Asterisk slave server pool (
http://home.comcast.net/~mroth01/LargeAsteriskSetup.gif )
- A TDM-VoIP gateway (Cisco, Quintum, AudioCodes, Lucent)
- Using Sangoma cards (As per David Mandelstam, Sangoma cards use
proprietary drivers and there are operational setups using 4 quads per
machine)
I'm not confident that the Asterisk software scales well under certain
conditions, such as using Monitor to digitally record 16 spans of voice
channels, so solving the card issue may not be the last step in a large
installation. If anyone has any insight on this, please post it to the
list.
Hope that was helpful,
Matthew Roth
http://www.voip-info.org/tiki-index.php?page=Running%20Asterisk%20on%20D
ebian
Matthew Boehm wrote:
>>From what I understand (and this could be completely wrong), the
Digium>cards use a bunch of processor interrupts and too many cards will use
up all>the interrupts. (again, that could be completely wrong).
>
>What kind of calls are they? G711->PRI? Not much CPU needed there. G729
->>PRI? Yes, you would need something along the lines of a dual Xenon
3.6Ghz do>do that. Its all in the transcoding. If just passthru, not much cpu is
>needed.
>
>-Matthew
>
>
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