ISUP release cause list

REL Cause Value	Meaning
	NORMAL EVENT CLASS
1	Unallocated number
2	No route to specified transit network
3	No route to destination
4	Send special information tone
5	Misdialled trunk prefix
6	Channel unacceptable
7	Call awarded and being delivered in an established channel
16	Normal call clearing
17	User busy
18	No user responding
19	No answer from user (user alerted)
20	Subscriber absent
21	Call rejected
22	Number changed
26	Non selected user clearing
27	Destination out of order
28	Invalid format (address incomplete)
29	Facility rejected
30	Response to status enquiry
31	Normal, unspecified
	RESOURCE UNAVAILABLE CLASS
34	No circuit/channel available
38	Network out of order
41	Temporary failure
42	Switching equipment congestion
43	Access information discarded
44	Request circuit/channel not available
47	Resource unavailable, unspecified
	SERVICE/OPTION NOT AVAILABLE CLASS
49	Quality of service unavailable
50	Requested facility not subscribed
55	Incoming calls barred within CUG
57	Bearer capability not authorized
58	Bearer capability not presently available
63	Service or option not available, unspecified
	SERVICE/OPTION NOT IMPLEMENTED CLASS
65	Bearer capability not implemented
69	Requested facility not implemented
70	Only restricted digital information                                                                                       bearer capability is available
79	Service or option not implemented, unspecified
	INVALID MESSAGE CLASS
81	Invalid call reference value
82	Identified channel does not exist
83	A suspend call existing but this call identity does not
84	Call identity in use
85	No call suspended
86	Call having the requested call identity has been cleared
87	User not member of CUG
88	Incompatible destination
91	Invalid transit network selection
95	Invalid message, unspecified
	PROTOCOL ERROR CLASS
96	Mandatory information element is missing
97	Message type non-existing or not implemented
98	Message not compatible with call state or                                                                            message type non-existing or not implemented
99	Information element non-existing or not implemented
100	Invalid information element contents
101	Message not compatible call state
102	Recovery on timer expiry
103	Parameter non-existent or not implemented
109	Unrecognized message has been passed on
110	Message with unrecognized parameter discarded
111	Protocol error, unspecified
	INTERWORK CLASS
127	Interworking, unspecified