Tech Stuff - Q.931 Cause Information Element

The Cause Information Element provides one or more octets that may help in diagnosing network or CPE problems.

Cause Format

The Cause IE is variable length with the following format:

8	7	6	5	4	3	2	1	Octet
0	Cause IE (0x08)							1
length of the Cause Information								2
1	coding std.		0	Location				3
1	Class			Value				4

NOTE: Bit 8 of octets 3 and 4 above is the Extension bit and is coded as follows:

Extension bit = 0 more information for this field follows.
Extension bit = 1 last octet of this field.

Coding Standard

7	6	Meaning
0	0	ITU standardized coding
1	1	Standard specific to Location field

Location

4	3	2	1	Meaning
0	0	0	0	User
0	0	0	1	Private network serving location user
0	0	1	0	Public network serving local user
0	0	1	1	Transit network
0	1	0	0	Public network serving remote user
0	1	0	1	Remote private network
0	1	1	1	International network
1	0	1	0	Network beyond interworking point

Class

7	6	5	Meaning
0	0	0	Normal event
0	0	1	Normal event
0	1	0	Resource unavailable
0	1	1	Service or option not available
1	0	0	Service or option not implemented
1	0	1	Invalid message (e.g. parameter out of range)
1	1	0	Protocol error (e.g. unknown error)
1	1	1	Interworking

Value

The Class and Value fields are normally treated as one. The following table shows the hexadecimal value with the extension bit set, without the extension bit set and the decimal value (without the extension bit set).

CCITT standard Values
Hex w Ext	Hex wo Ext	Dec	Meaning
0x81	0x01	1	Unassigned number
0x82	0x02	2	No route to specified network
0x83	0x03	3	No route to specified transit network
0x86	0x06	6	Channel Unacceptable
0x87	0x07	7	Call awarded and being delivered in an established channel
0x90	0x10	16	Normal, clearing
0x91	0x11	17	User busy
0x92	0x12	18	No user responding
0x93	0x13	19	User alterting
0x95	0x15	21	Call rejected
0x96	0x16	22	Number changed
0x9A	0x1A	26	Non-selected user clearing
0x9B	0x1B	27	Destination out of order
0x9C	0x1C	28	Invalid number format (incomplete)
0x9D	0x1D	29	Requested facility rejected
0x9E	0x1E	30	Response to STATUS ENQuiry
0x9F	0x1F	31	Normal, unspecified
0xA2	0x22	34	No channel available
0xA3	0x23	35	Call queued
0xA9	0x29	41	Temporary failure
0xAA	0x2A	42	Network congestion
0xAB	0x2B	43	Access information discarded
0xAC	0x2C	44	Requested channel not available
0xAF	0x2F	47	Resource unavailable, unspecified
0xB2	0x32	50	Requested facility not subscribed
0xB9	0x39	57	Beare capability not authorized
0xBA	0x3A	58	Bearer capability not presently available
0xBF	0x3F	63	Service or option not available
0xC1	0x41	65	Bearer service not implemented
0xC5	0x45	69	Requested facility not implemented
0xCF	0x4F	79	Service or option not implemented, unspecified
0xD2	0x52	81	Invalid call reference
0xD8	0x58	88	Incompatible destination
0xE0	0x60	96	Mandatory IE missing
0xE1	0x61	97	Message type non-existent or not imp-lemented
0xE3	0x63	99	Information element non-existent or not implemented
0xE4	0x64	100	Invalid IE contents
0xE5	0x65	101	Message not compatible with call state
0xE6	0x66	102	Recovery of timer expiry
0xEF	0x6F	111	Protocol error, unspecified
0xFF	0x7F	127	Interworking, unspecified
National Specific
0x84	0x04	4	Vacant code
0x88	0x08	8	Prefix 0 dialed in error
0x89	0x09	9	Prefix 1 dialed in error
0x8A	0x0A	10	Prefix 1 not dialed
0x8B	0x0B	11	Excessive digits received, call is proceeding
Network Specific
0x88	0x08	8	Call is proceeding
0x8D	0x0D	13	Service denied
0x9C	0x1C	28	Special Intercept Announcement
0x9D	0x1D	29	Special Intercept announcement, undefined code
0x9E	0x1E	30	Special Intercept announcement, number unassigned
0x9F	0x1F	31	Special intercept annoucement, call blocked due to group restriction
0xA3	0x23	35	Blocked due to group restrictions, call queued
0xB3	0x33	51	Call type incompatible with service request
0xB5	0x35	53	Service operation violated
0xE5	0x65	101	Protocol error, threshold exceeded
Custom Lucent
0xB4	0x34	52	Outgoing calls barred
0xB6	0x36	54	Incoming calls barred
0xC2	0x42	66	Channel type not implemented
0xD3	0x53	82	Identified channel does not exist
0xDB	0x5B	91	Transit network does not exist
0xE2	0x62	98	Message not compatible with call state

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