Summary:ASTERISK-25034: chan_dahdi: Some telco switches occasionally ignore ISDN RESTART requests.
Reporter:Richard Mudgett (rmudgett)Labels:
Date Opened:2015-04-29 13:35:41Date Closed:2015-04-30 11:12:15
Versions:11.17.1 13.3.2 Frequency of
is related toASTERISK-19608 Asterisk-1.8.x starts rejecting calls with cause code 44 after some time.
Description:The fix for ASTERISK-19608 added an escape clause for B channels in the restarting state if the telco ignores a RESTART request.  If the telco fails to acknowledge the RESTART then Asterisk will assume the telco acknowledged the RESTART on the second call attempt requesting the B channel by the telco.  The escape clause is good for dealing with RESTART requests in general but it does cause the next call for the restarting B channel to be rejected if the telco insists the call must go on that B channel.

chan_dahdi doesn't really need to issue a RESTART request in response to receiving a cause 44 (Requested channel not available).  Sending the RESTART in such a situation is not required (nor prohibited) by the standards.  I think chan_dahdi does this for historical reasons to deal with buggy peers to get channels unstuck in a similar fashion as the chan_dahdi.conf resetinterval option.

This issue proposes to add a chan_dahdi.conf force_restart_unavailable_chans compatability option that when disabled will prevent chan_dahdi from trying to RESTART the channel in response to a cause 44 code.
Comments:By: Richard Mudgett (rmudgett) 2015-04-29 18:19:47.326-0500

Patches up on gerrit:
v11 https://gerrit.asterisk.org/#/c/303/
v13 https://gerrit.asterisk.org/#/c/304/
master https://gerrit.asterisk.org/#/c/305/