Q.931 Cause

Q.931 Cause (ITU Q.931 section 4.5.12，定義在 Q.850)

8	7	6	5	4	3	2	1	Octet
IE ID: 0x08								1
Length								2
ext. 0/1	Coding Std.		0	Location				3
ext. 1	Recommendation							3a
ext. 1	Cause Value							4
Diagnostic(s)								5

• Coding Standard：編碼標準，無法度用 ITU-T 標準才使用其它標準。
• 0 = ITU-T 標準
• 1 = ISO/IEC 標準
• 2 = national 標準
• 3 = standard specific to identified location
• Location
• 0 = user (U)
• 1 = private network serving the local user (LPN)
• 2 = public network serving the local user (LN)
• 3 = transit network (TN)
• 4 = public network serving the remote user (RLN)
• 5 = private network serving the remote user (RPN)
• 7 = international network (INTL)
• 10 = network beyond interworking point (BI)
• 12~15：reserved for national use
• 其它：spare
• Cause Value：其中 bit 7~5 是 class 分類，表示 the general nature of the event。如下表：

Class	Hex	Dec	Cause
0, 1 = normal	01	1	Unallocated or unassigned number
	02	2	No route to specified transit network (Transit Network Identity)
	03	3	No route to destination
	04	4	Send special information tone
	05	5	Misdialed trunk prefix
	06	6	Channel unacceptable
	07	7	Call awarded and being delivered in an established channel
	08	8	Prefix 0 dialed but not allowed
	09	9	Prefix 1 dialed but not allowed
	0A	10	Prefix 1 not dialed but required
	0B	11	More digits received than allowed, call is proceeding
	10	16	Normal call clearing. 如果是呼叫失敗，可能是高層協定 (如 PPP)、認證、或 idle timeout 相關問題。Also, if you have requested a callback, the remote device disconnects the call, generates this code, and then calls you back.
	11	17	User busy
	12	18	No user responding
	13	19	T.301 expired: – User Alerted, No answer from user
	15	21	Call rejected
	16	22	Number changed to number in diagnostic field.
	17	23	Reverse charging rejected
	18	24	Call suspended
	19	25	Call resumed
	1A	26	Non-selected user clearing
	1B	27	Destination out of order
	1C	28	Invalid number format or incomplete address
	1D	29	EKTS facility rejected by network
	1E	30	Response to STATUS INQUIRY
	1F	31	Normal, unspecified
2 = resource unavailable	21	33	Circuit out of order
	22	34	No circuit/channel available
	23	35	Destination unattainable
	24	36	Out of order
	25	37	Degraded service
	26	38	Network out of order
	27	39	Transit delay range cannot be achieved
	28	40	Throughput range cannot be achieved
	29	41	Temporary failure
	2A	42	Switching equipment congestion
	2B	43	Access information discarded
	2C	44	Requested circuit channel not available
	2D	45	Preempted
	2E	46	Precedence call blocked
	2F	47	Resource unavailable, unspecified
3 = service or option not available	31	49	Quality of service unavailable
	32	50	Requested facility not subscribed
	33	51	Reverse charging not allowed
	34	52	Outgoing calls barred
	35	53	Outgoing calls barred within CUG
	36	54	Incoming calls barred
	37	55	Incoming calls barred within CUG
	38	56	Call waiting not subscribed
	39	57	Bearer capability not authorized
	3A	58	Bearer capability not presently available
	3F	63	Service or option not available, unspecified
4 = service or option not implemented	41	65	Bearer service not implemented
	42	66	Channel type not implemented
	43	67	Transit network selection not implemented
	44	68	Message not implemented
	45	69	Requested facility not implemented
	46	70	Only restricted digital information bearer capability is available
	4F	79	Service or option not implemented, unspecified
5 = invalid message	51	81	Invalid call reference value
	52	82	Identified channel does not exist
	53	83	A suspended call exists, but this call identity does not
	54	84	Call identity in use
	55	85	No call suspended
	56	86	Call having the requested call identity has been cleared
	57	87	Called user not member of CUG
	58	88	Incompatible destination
	59	89	Non-existent abbreviated address entry
	5A	90	Destination address missing, and direct call not subscribed
	5B	91	Invalid transit network selection (national use)
	5C	92	Invalid facility parameter 93 Mandatory information element is missing
	5D	93	Message type non-existent or not implemented
	5F	95	Invalid message, unspecified
6 = protocol error	60	96	Mandatory information element is missing
	61	97	Message type non-existent or not implemented
	62	98	Message not compatible with call state or message type non-existent or not implemented
	63	99	Information element nonexistent or not implemented
	64	100	Invalid information element contents
	65	101	Message not compatible with call state
	66	102	Recovery on timer expiry
	67	103	Parameter non-existent or not implemented – passed on
	6F	111	Protocol error, unspecified
7 = interworking	7F	127	Internetworking, unspecified
?	80 +	128 +	Proprietary diagnostic code (not necessarily bad). Typically used to pass proprietary control or maintenance messages between multiplexers.

範例

08 02 81 90：Class 0 Value 0

08 03 81 e2 0f ：Class 6 Value 2

參考

• https://www.viavisolutions.com/en-us/support/files/Q.931-Cause-Codes