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failure to answer some calls


ndemou
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Every once in a while a few users complain that they can't answer incoming calls. From their point of view they pick up the handset and it's like there was no call. I was able to trace 3 failed calls in two different domains (and kept detailed pcap traces and logs for the last one of them).

SIP trace with carrier
======================
|Time     | carrier GW                            |
|         |                   |          PBX      |                   
|0,000    |         INVITE SDP                    |SIP From: Anonymous ...
|         |(5060)   ------------------>  (5060)   |
|0,002    |         100 Trying|                   |SIP Status
|         |(5060)   <------------------  (5060)   |
|0,010    |         200 Ok SDP                    |SIP Status
|         |(5060)   <------------------  (5060)   |
|0,032    |         ACK       |                   |SIP Request
|         |(5060)   ------------------>  (5060)   |
|11,980   |         BYE       |                   |SIP Request
|         |(5060)   <------------------  (5060)   |
|11,990   |         200 OK    |                   |SIP Status
|         |(5060)   ------------------>  (5060)   |

SIP trace with VoIP phone
=========================
|Time     | PBX                                   |
|         |                   |     VoIP Phone    |                   
|0,000    |         INVITE SDP                    |SIP From: "Anonymous"...
|         |(5060)   ------------------>  (1036)   |
|0,053    |         100 Trying|                   |SIP Status
|         |(5060)   <------------------  (1036)   |
|0,185    |         180 Ringing                   |SIP Status
|         |(5060)   <------------------  (1036)   |
|5,482    |         200 OK SDP                    |SIP Status
|         |(5060)   <------------------  (1036)   |
|5,483    |         ACK       |                   |SIP Request
|         |(5060)   ------------------>  (1036)   |
|5,547    |         BYE       |                   |SIP Request
|         |(5060)   ------------------>  (1036)   |
|5,626    |         200 OK    |                   |SIP Status
|         |(5060)   <------------------  (1036)   |

So the PBX got a 200 OK from the phone and a few milisecs later it send a BYE back to the phone and to the carrier dropping the call. Looking at the logs to see why I see this:

[8] 20140716134853: Call state for call object 143211: alerting
[...]
[...]
[8] 20140716134854: call port 22: state code from 100 to 200
[8] 20140716134854: call port 20: state code from 200 to 200
[7] 20140716134854: 14675947-3614496522-991048@carrier: RTP pass-through mode
[7] 20140716134854: 1e4c6746@pbx: RTP pass-through mode
[7] 20140716134854: Determine pass-through mode after receiving response
[8] 20140716134854: Call state for call object 143211: connected
[...]
[8] 20140716134854: call port 20: state code from 200 to 486
[8] 20140716134854: call port 22: state code from 200 to 486
[...]
[...]
[7] 20140716134855: Call 14675947-3614496522-991048@carrier: Clear last request
[5] 20140716134855: BYE Response: Terminate 14675947-3614496522-991048@carrier
[7] 20140716134855: 1e4c6746@pbx: Media-aware pass-through mode
[8] 20140716134855: Clearing call port 20, SIP call id 14675947-3614496522-991048@carrier
[8] 20140716134855: Remove leg 347938: call port 20, SIP call id 14675947-3614496522-991048@carrier
[7] 20140716134855: Call 1e4c6746@pbx: Clear last request
[5] 20140716134855: BYE Response: Terminate 1e4c6746@pbx
[8] 20140716134855: Clearing call port 22, SIP call id 1e4c6746@pbx
[8] 20140716134855: Remove leg 347940: call port 22, SIP call id 1e4c6746@pbx

I've noticed that call port 22 that correspond to this call goes from 100 to 200 and almost immediately after that from 200 to 486. I guess these numbers correspond to SIP status so the 486 (busy) seems really strange to me. This (BYE send from pbx and log lines like the above) happened in all 3 cases that I was able to follow closely.

 

I can provide the pcap traces and full log if needed (I just can't post them publicly)

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