[Freeswitch-users] [REQUESTED_CHAN_UNAVAIL] error with Sangoma FreeTDM

[Neil Patel]

Hi All,

Several of my PRIs in India have recently been getting this error from time
to time. Every time it happens, I can temporarily fix it by restarting FS:

2014-02-03 13:11:25.713142 [NOTICE] mod_freetdm.c:2728 Hangup
FreeTDM/3:4/0942847XXXX [CS_INIT] [REQUESTED_CHAN_UNAVAIL]
2014-02-03 13:11:25.713142 [DEBUG] switch_ivr_originate.c:3639 Originate
Resulted in Error Cause: 44 [REQUESTED_CHAN_UNAVAIL]

Our system sends 30 calls at a time to the PRI gateway, and this error
comes up on any one of the channels. The channel is not in use at the time,
based on 'show channels'. FreeTDM does not bypass the channel and try
another, so if it's channel 14 that's unavailable it doesn't move on to 15,
and only 1-14 get used (until I restart FS).

Sangoma support has examined a trace and found the d-channel on affected
lines fluctuating. Also I notice that around the time this problem crops up
the line suddenly flicks signals:

2014-02-03 17:25:00.877663 [DEBUG] ftmod_sangoma_isdn_cntrl.c:45
[s2c1][2:1] Signalling link status changed to UP
2014-02-03 17:25:00.877663 [DEBUG] ftmod_sangoma_isdn_cntrl.c:45
[s2c2][2:2] Signalling link status changed to UP
2014-02-03 17:25:00.877663 [DEBUG] ftmod_sangoma_isdn_cntrl.c:45
[s2c3][2:3] Signalling link status changed to UP
2014-02-03 17:25:00.877663 [DEBUG] ftmod_sangoma_isdn_cntrl.c:45
[s2c4][2:4] Signalling link status changed to UP
2014-02-03 17:25:00.877663 [DEBUG] ftmod_sangoma_isdn_cntrl.c:45
[s2c5][2:5] Signalling link status changed to UP
...

I'm also wondering whether I should give a time gap between originate
commands? Perhaps inserting a half second or so between calls will prevent
the channels from getting jammed up.

I'm not sure where the issue lies. With the telco (fluctuating d-channel),
with FreeTDM, perhaps with my Sangoma hardware or driver (currently running
7.0.8 and libsng_isdn 7.28.0)?

Thanks,
Neil
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