Common Causes for BRI/PRI Outgoing Call Failure

Symptom

Failed to make outbound calls from BRI/PRI line

Common Causes

Firstly you would need to know how to get the BRI/PRI packets.

U-Series/Gateway: BRI/PRI debug for U-Series
S-Series: BRI/PRI debug for S-Series
For S-Series, you can also try System Log with PRI debug option enabled: System Log

Then you need to understand the BRI/PRI call flow and a few elements in Q.931 messages by followed this article: A Brief View of the PRI Call Flow

1. Incorrect DOD Setting

You might receive Hangup cause in DISCONNECT message like the following:

[2018-11-28 18:35:07] PRI Span: 2 < Cause (len= 5) [ Ext: 1  Coding: CCITT (ITU) standard (0)  Spare: 0  Location: Public network serving the local user (2)

[2018-11-28 18:35:07] PRI Span: 2 <                  Ext: 1  Cause: Invalid information element contents (100), class = Protocol Error (e.g. unknown message) (6) ]
 To fix this issue, please fill the correct DOD in the BRI/PRI trunk setting.

2. Incorrect TON (Type of Number)

- If you don't which TON to use, please use Unknown.

- If your inbound calls are working, you can refer the TON used in the incoming SETUP message. Then adjust the TON on the BRI/PRI trunk settings.

< Message Type: SETUP (5)
< [04 03 90 90 a3]
< Bearer Capability (len= 5) [ Ext: 1 Coding-Std: 0 Info transfer capability: 3.1kHz audio (16)
< Ext: 1 Trans mode/rate: 64kbps, circuit-mode (16)
< User information layer 1: A-Law (35)
< [18 03 a9 83 82]
< Channel ID (len= 5) [ Ext: 1 IntID: Implicit Other(PRI) Spare: 0 Exclusive Dchan: 0
< ChanSel: As indicated in following octets
< Ext: 1 Coding: 0 Number Specified Channel Type: 3
< Ext: 1 Channel: 2 Type: CPE]
< [1e 02 82 88]
< Progress Indicator (len= 4) [ Ext: 1 Coding: CCITT (ITU) standard (0) 0: 0 Location: Public network serving the local user (2)
< Ext: 1 Progress Description: Inband information or appropriate pattern now available. (8) ]
< [6c 0d 41 83 31 33 35 30 31 38 33 36 38 36 35]
< Calling Party Number (len=15) [ Ext: 0 TON: Subscriber Number (4) NPI: ISDN/Telephony Numbering Plan (E.164/E.163) (1)
< Presentation: Presentation allowed, Network provided (3) '13501836865' ]

< [70 09 c1 35 31 30 36 34 32 37 36]
< Called Party Number (len=11) [ Ext: 1 TON: Subscriber Number (4) NPI: ISDN/Telephony Numbering Plan (E.164/E.163) (1) '51064276' ]

 

3. Incorrect Codec

Same as last one, refer the SETUP message and select the same codec in the incoming SETUP message.

< Message Type: SETUP (5)
< [04 03 90 90 a3]
< Bearer Capability (len= 5) [ Ext: 1 Coding-Std: 0 Info transfer capability: 3.1kHz audio (16)
< Ext: 1 Trans mode/rate: 64kbps, circuit-mode (16)
< User information layer 1: A-Law (35)
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