Congestion() Forcing PRI Channels To Be Not Available

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Asterisk Users 3 Comments

Hi, I have a PSTN Asterisk box that’s connected to other dialplan PBXes through IAX2.

Recently this box was upgraded to 1.4.44 with the latest DAHDI version. I’ve noticed that if one of the dialplan PBXes calls Congestion(), the PRI
will return ISDN code 34 (as its supposed to do). However, the issue is that subsequent calls into that PRI channel are immediately responded by a Code 44 (channel not available) even though there is no live call on the channel.

Has anyone else experienced this behavior? Its a pretty crippling behavior since all of our channels eventually become unresponsive until a ‘dahdi restart’ is issued.


— James

3 thoughts on - Congestion() Forcing PRI Channels To Be Not Available

  • I believe that what you are describing is a very old bug, which is fixed somewhere in the 1.8 timeline when the interface between DAHDI and Asterisk is changed slightly. I encountered the same issue some time ago. I do not recall the exact conditions under which the issue happens, but I believe it is the attempt to cancel an unanswered inbound call with a specific subset of cause codes.

    If you are using an older Asterisk version, the only workaround is to use Playtones + Hangup() instead of sending the Congestion() or Busy() cause codes.

    Regards, Steve

  • It must have been introduced between DAHDI 2.4.0 and 2.6.1 or between Asterisk 1.4.35 and 1.4.44. I had a box running Asterisk 1.4.35 + DAHDI 2.4.0 and I never had any issues.

    — James