Occasionally "all circuits are busy now", altough enough lines are available

Hello,

occasionally our users report getting “all circuits are busy now”, although we have enough lines available.

We have 4 ISDN channels, so 8 parallel calls should be possible:

voip*CLI> dahdi show channels
Chan Extension Context Language MOH Interpret Blocked State Description
pseudo default default In Service
1 from-digital de default In Service
2 from-digital de default In Service
4 from-digital de default In Service
5 from-digital de default In Service
7 from-digital de default In Service
8 from-digital de default In Service
10 from-digital de default In Service
11 from-digital de default In Service

Log Excerpt:
[2015-01-26 10:03:43] VERBOSE[2373] chan_sip.c: Really destroying SIP dialog ‘[email protected]:5060’ Method: OPTIONS
[2015-01-26 10:03:44] VERBOSE[2407][C-000011b6] sig_pri.c: – Span 1: Channel 0/1 got hangup request, cause 34
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] app_dial.c: – DAHDI/i1/0177XXXXXXX-532 is circuit-busy
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] chan_dahdi.c: – Hungup ‘DAHDI/i1/0177XXXXXXX-532’
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] app_dial.c: == Everyone is busy/congested at this time (1:0/1/0)
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] pbx.c: – Executing [[email protected]:2] GotoIf(“SIP/43-00001bf6”, “0?emergency,1”) in new stack
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] pbx.c: – Executing [[email protected]:3] GotoIf(“SIP/43-00001bf6”, “0?intracompany,1”) in new stack
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] pbx.c: – Executing [[email protected]:4] Playback(“SIP/43-00001bf6”, “all-circuits-busy-now&pls-try-call-later, noanswer”) in new stack
[2015-01-26 10:03:44] VERBOSE[10836][C-000011b6] file.c: – <SIP/43-00001bf6> Playing ‘all-circuits-busy-now.slin’ (language ‘de’)

I checked the given time and there was only 1 incoming call at this time, so I don’t understand why it gives me “all circuits are busy now”. A few seconds later another try the call worked. It happens rarely, but often enough to annoy users.

Any Idea to dig into this problem?

search this space for ‘glare’

So the problem may be collision. I’ll try to use trunk G0 instead of g0 with Group 0 Descending then.

Although I don’t understand why the freepbx wiki states collision on analog lines. As far as I understand, ISDN is not analog actually.

Maybe it helps.

Well. that’s true but you have multiple BRI’s so they are granular by only two not eight, the d-channel is the arbitrator of available b-channels within that span, and there are many variations of ISDN signalling choices that can and will occasionally throw up a “glare” condition, perhaps if a simultaneous inbound call appears on the d-channel, you are clean out of b-channels and you loose :wink: , you will even see that less occasionally on PRI’s, but they have more redundancy so tend to recover to another b-channel without call loss, it is always good policy to have your outbound calls hunt conversely to your inbound calls both within the span and within the “group” container.