[asterisk-users] Maximum number of PRI calls on 1 asterisk box (no HW echo)

[Tzafrir Cohen]

On Thu, Mar 25, 2010 at 10:24:41AM -0600, Carlos Chavez wrote:
> On Thu, 2010-03-25 at 17:11 +0100, Christian Victor wrote:
> > Hi James,
> > 
> > we did sucessfully run two TE410P with 8xE1 in a decent Intel P4-3200
> > machine with quite heavy line usage. No codec conversion course.
> > 
> > I don't believe that there is a hard limit of E1s coded into Asterisk.
> > But the maximum lines you can squeeze out of your specific hardware
> > depends on so many factors (asterisk version, hardware etc).
> > 
> > Chris
> > 
> 	If you ever take the DCAP training they use a single server with 16 T1
> Spans (4 quad cards) and a 24 port analog card to provide connectivity
> to the participants.  That means that they have 5 cards and 17 spans for
> all ports.  Obviously there is not much load on the system because they
> are not using all channels at once.  Asterisk can handle all those ports
> so there does not seem to be a set limit as there was in the 1.0 days
> where you could not have more 250 zap devices.

The "limit" of 250 (actually 249. It was 250 originally and changed to
249 when /dev/zap/transcode was introduced) zap channels is only that of
the device files that are generated. But userspace programs normally use
/dev/dahdi/channel to ask for a channel (using the ioctl DAHDI_SPECIFY)
and don't need to open /dev/dahdi/NNN directly (but if that really
bothers you, that limitation has been removed in the branhc
/team/tzafrir/sysfs ).

Asterisk, though, has an arrach of 32 'spans' (PRI spans). This means
that if you try using a PRI span number whose number >= 32 you'll get an
annoying error.

Someone who encontered that error early on was KP Junghanns. He added
support for BRI devices to chan_zap. Thus he had much smaller spans. And
could afford inclding many of them (a single octobri card has 8 spans).
Which is why the bristuff patch includes the following:

-#define NUM_SPANS              32
+#define NUM_SPANS              128     /*!<"32 spans", muahahaha, us alaws like to have some more... */

In the Debian package I incllude a slightly different variant of it:

-#define NUM_SPANS 		32
+#define NUM_SPANS 		DAHDI_MAX_SPANS

As you can see, there's actually a limit at the DAHDI level.
DAHDI_MAX_SPANS, which is 128. Likewise there's DAHDI_MAX_CHANS which is
1024. That's as many channels that you can have. 

(Disclaimer: I may be off by one here and there, as DAHDI span numbers
and channel numbers are 1-based rather than 0-based)

If you need more, you'll just have to rebuild DAHDI (been there, done
that ;-)

-- 
               Tzafrir Cohen
icq#16849755              jabber:tzafrir.cohen at xorcom.com
+972-50-7952406           mailto:tzafrir.cohen at xorcom.com
http://www.xorcom.com  iax:guest at local.xorcom.com/tzafrir