You are here: CSP Developer’s Guide: Common Channel Signaling > A Appendix > Cause Codes

Cause Codes

Overview

The following cause values, names and definitions are identified in Q.850 as pertaining to ISUP.

ITU Standard Causes

The following cause values, names and definitions are identified in Q.850 as pertaining to ISUP.

NORMAL CLASS

Cause 1 Unallocated (unassigned) number - This cause indicates that the called party cannot be reached because, although the called party number is in a valid format, it is not currently allocated (assigned).

Cause 2 No route to specified transit network - This cause indicates that the equipment sending this cause has received a request to route the call through a particular transit network which it does not recognize. The equipment sending this cause does not recognize the transit network either because the transit network does not exist or because that particular transit network, while it does exist, does not serve the equipment that is sending this cause. This cause is supported on a network dependent basis.

Cause 3 No route to destination - This cause indicates that the called party cannot be reached because the network through which the call has been routed does not serve the destination desired. This cause is supported on a network-dependent basis.

Cause 4 Send special information tone - This cause indicates that the called party cannot be reached for reasons that are of long term nature and that the special information tone should be returned to the calling party.

Cause 5 Misdialed trunk prefix - No procedures specified for US networks.

Cause 8 Preemption - This cause indicates that the call is being preempted.

Cause 9 Preemption - Circuit reserved for reuse. This cause indicates that the call is being preempted and the circuit is reserved for reuse by the preempting exchange.

Cause 16 Normal call clearing - This cause indicates that the call is being cleared because one of the users involved in the call has requested that the call be cleared. Under normal situations, the source of this cause is not the network.

Cause 17 User busy - This cause is used to indicate that the called party is unable to accept another call because the user busy condition has been encountered. This cause value may be generated by the called user or by the network. In the case of user determined user busy, it is noted that the user equipment is compatible with the call.

Cause 18 No user responding - This cause is used when a called party does not respond to a call establishment message with either an alerting or connect indication within the prescribed period of time allocated.

Cause 19 No answer from user (user alerted) - This value is used when the called party has been alerted but does not respond with a connect indication within a prescribed period of time. Note - This cause is not necessarily generated by Q.93l procedures but may be generated by internal network timers.

Cause 20 Subscriber absent - This cause value is used when a mobile station has logged off, radio contact is not obtained with a mobile station or if a personal telecommunication user is temporarily not addressable at any user-network interface.

Cause 21 Call rejected - This cause indicates that the equipment sending this cause does not wish to accept this call, although it could have accepted the call because the equipment sending this cause is neither busy nor incompatible. The network may also generate this cause, indicating that the call was cleared due to a supplementary service constraint. The diagnostic field may contain additional information about the supplementary service and reason for rejection.

Cause 22 Number changed - This cause is returned to a calling party when the called party number indicated by the calling party is no longer assigned. The new called party number may optionally be included in the diagnostic field. If a network does not support this cause value, cause number 1, unallocated (unassigned) number shall be used.

Cause 27 Destination out of order - This cause indicates that the destination indicated by the user can not be reached because the interface to the destination is not functioning correctly. The term "not functioning correctly" indicates that a signaling message was unable to be delivered to the remote party; e.g., a physical layer or data link layer failure at the remote party, or user equipment off-line.

Cause 28 Invalid number format (address incomplete) - This cause indicates that the called party cannot be reached because the called party number is not in a valid format or is not complete.

This condition may be determined:

• Immediately after reception of an ST signal, or

• On time-out after the last received digit.

Cause 29 Facility rejected - This cause is returned when the network cannot provide a supplementary service requested by the user.

Cause 31 Normal, unspecified - This cause is used to report a normal event only when no other cause in the normal class applies.

Resource Unavailable Class

Cause 34 No circuit/channel available - This cause indicates that there is no appropriate circuit/channel presently available to handle the call.

Cause 38 Network Out of order - This cause indicates that the network is not functioning correctly and that the condition is likely to last a relatively long period of time, e.g., immediately re-attempting the call is not likely to be successful.

Cause 41 Temporary failure - This cause indicates that the network is not functioning correctly and that the condition is not likely to last a long period of time, e.g., the user may wish to try another call attempt almost immediately.

Cause 42 Switching equipment congestion - This cause indicates that the switching equipment generating this cause is experiencing a period of high traffic.

Cause 43 Access information discarded - This cause indicates that the network could not deliver access information to the remote user as requested, i.e., user-to-user information, low layer compatibility, high layer compatibility, or sub-address, as indicated in the diagnostic. It is noted that the particular type of access information discarded is optionally included in the diagnostic.

Cause 44 Requested circuit/channel not available - This cause is returned when the circuit or channel indicated by the requesting entity cannot be provided by the other side of the interface.

Cause 46 Precedence call blocked - This cause indicates that there are no preemptable circuits or that the called user is busy with a call of equal or higher preemptable level.

Cause 47 Resource unavailable, unspecified - This cause is used to report a resource unavailable event only when no other cause in the resource unavailable class applies.

SERVICE OR OPTION UNAVAILABLE CLASS

Cause 50 Requested facility not subscribed - This cause indicates that the user has requested a supplementary service that is implemented by the equipment that generated this cause, but the user is not authorized to use.

Cause 53 Outgoing calls barred within CUG – No procedure specified for US networks.

Cause 55 Incoming calls barred within CUG –

No procedure specified for US networks.

Cause 57 Bearer capability not authorized -

This cause indicates that the user has requested a bearer capability that is implemented by the equipment that generated this cause, but the user is not authorized to use.

Cause 58 Bearer capability not presently available -

This cause indicates that the user has requested a bearer capability that is implemented by the equipment which generated this cause but which is not available at this time.

Cause 62 inconsistency in designated outgoing access information and subscriber class -

This cause indicates that there is an inconsistency in the designated outgoing access information and subscriber class.

Cause 63 Service or option not available, unspecified -

This cause is used to report a service or option not available event only when no other cause in the service or option not available class applies.

SERVICE/OPTION NOT IMPLEMENTED CLASS

Cause 65 Bearer capability not implemented - This cause indicates that the equipment sending this cause does not support the bearer capability requested.

Cause 69 Requested facility not implemented - This cause indicates that the equipment sending this cause does not support the requested supplementary service.

Cause 70 Only restricted digital information bearer capability is available - This cause indicates that the calling party has requested an unrestricted bearer service but that the equipment sending this cause only supports the restricted version of the requested bearer capability.

Cause 79 Service or option not implemented, unspecified - This cause is used to report a service or option not implemented event only when no other cause in the service or option not implemented class applies.

INVALID MESSAGE (E.G. PARAMETER OUT OF RANGE) CLASS

Cause 87 User not member of CUG – No procedures specified for US networks.

Cause 88 Incompatible destination - This cause indicates that the equipment sending this cause has received a request to establish a call which has low layer compatibility, high layer compatibility, attributes (e.g., data rate) which can not be accommodated.

Cause 90 Non-existent CUG – No procedures specified for US networks.

Cause 91 Invalid transit network selection - This cause indicates that a transit network identification was received which is of an incorrect format as defined in Annex C of TI.607

Cause 95 Invalid message, unspecified - This cause is used to report an invalid message event only when no other cause in the invalid message class applies.

Protocol Error (e.g. Unknown Message) Class

Cause 97 Message type non-existent or not implemented -

This cause indicates that the equipment sending this cause has received a message with a message type it does not recognize either because this is a message not defined or defined but not implemented by the equipment sending this cause.

Cause 99 Information Element/Parameter non-existent or not implemented -

This cause indicates that the equipment sending this cause has received a message which includes information element(s)/parameter(s) not recognized because the information element identifier(s)/parameter name(s) are not defined or are defined but not implemented by the equipment sending the cause. This cause indicates that the information element(s)/parameter(s) were discarded. However, the information element is not required to be present in the message in order for the equipment sending the cause to process the message.

Cause 102 Recovery on timer expiry -

This cause indicates that a procedure has been initiated by the expiry of a timer in association with error handling procedures.

Cause 103 Parameter non-existent or not implemented – pass on –

No procedures specified for US networks.

Cause 110 Message with unrecognized parameter discarded -

This cause indicates that the equipment sending this cause has discarded a received message which includes a parameter that is not recognized.

Cause 111 Protocol error unspecified -

This cause is used to report a protocol error event only when no other cause in the protocol error class applies.

INTERWORKING CLASS

Cause 127 Interworking, unspecified -This cause indicates that there has been interworking with a network which does not provide causes for actions it takes. Thus, the precise cause for a message that is being sent cannot be ascertained.

ANSI Standard Causes

The following cause values, names and definitions are identified in ____ as pertaining to ISUP.

NORMAL CLASS

Cause 23 Unallocated destination number - This cause indicates failure of a business group call because the business group identifier is unknown.

Cause 24 Undefined business group - This cause indicates failure of a business group call because the destination number is unallocated in the business group numbering plan.

Cause 25 Exchange routing error - This cause indicates that the called party cannot be reached because of an error in exchange number translation tables used to route the call (results when the hop counter parameter value is decremented to 0).

RESOURCE UNAVAILABLE CLASS

Cause 45 Preemption - (Used by T1.113-1988 and Tl.619-1992.) This cause indicates that the equipment sending this cause has preempted the circuit for a new call and the existing call should be cleared.

Cause 46 Precedence call blocked - (Used by T1.113-1988 and T1.169-1992.) In case of a call with a precedence level higher than the lowest level (ROUTINE), this cause indicates that all circuits are busy on calls of equal or higher priority.

SERVICE OR OPTION NOT AVAILABLE CLASS

Cause 51 Call type incompatible with service request - This cause indicates that an action was rejected because it was not compatible with the bearer capability of the call.

Cause 54 Call blocked due to group restrictions -

This cause indicates failure of a business group call because it did not pass line privileges and/or subgroup screening.

See Integrated Services Digital Network User Part.
International Telecommunications Union (UN)
In PPL, a condition that, when met, drives a state machine (PPL Component) from one state to another, by invoking an associated Primitive. In PPL files, an Event is marked by an arrow and text.
Interworking is a software feature within the Excel platform call control layer that enables protocol conversion by analyzing and converting Network Signaling (NS) Layer 3 information.
American National Standards Institute. ANSI administers and coordinates the U.S. voluntary standardization and conformity assessment system for the
telecommunications industry. More details on these standards may be
viewed at www.ansi.org.
Digital communications link - voice, data, and video at a 1.544 Mbps rate (24 64 Kbps channels)
ISDN User Part (ISUP)