GSM 09.02 - Version 5.3.0 - Digital cellular telecommunications - ETSI

MS Not Reachable
The MS may not be reachable for the following reasons:
- there is no location information available for the MS;
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GSM 09.02 Version 5.3.0: August 1996
- the MSC Area Restricted Flag is set, indicating that roaming in the MSC area is not allowed;
- the "MS purged" flag is set, indicating that the MS data have been purged from the VLR;
- the Provide Roaming Number procedure fails and returns the error Absent Subscriber;
- the Provide Roaming Number procedure fails and returns the error "No Roaming Number Available".
The HLR will then check if the service Call Forwarding on MS Not Reachable is active. If the service is not
active the appropriate user error ("System Failure" if the VLR returned "No Roaming Number Available",
otherwise "Absent Subscriber") is returned to the Gateway MSC. This is contained in the
MAP_SEND_ROUTING_INFORMATION service response. The procedure in the HLR is then terminated.
If the Call Forwarding on MS Not Reachable service is active, the call has not been forwarded more times
than allowed and a CUG call authorization check is not required, the HLR will increment the forwarding
counter and provide the routing information for forwarding this call.
If the Call Forwarding on MS Not Reachable service is active and CUG information is provided and/or the
forwarding subscriber is a CUG subscriber then the HLR will perform a CUG call authorization check on the
forwarding party's outgoing access. The procedures for authorizing a CUG check with Call Forwarding
interaction are described in more detail in TS GSM 03.85. On successful completion of the authorization
check, the HLR will increment the forwarding counter and provide the routing information for forwarding this
call. The new CUG Information (i.e. output of the CUG call authorization check) to be used on the
forwarding leg of the call will also be provided.
This forwarding information is returned to the Gateway MSC in the
MAP_SEND_ROUTING_INFORMATION service response. The procedure in the HLR is then terminated.
Forwarding Violation
If a Call Forwarding service is active, but the call has already been forwarded as many times as allowed,
the user error "Forwarding Violation" is returned to the Gateway MSC. This is contained in the
MAP_SEND_ROUTING_INFORMATION service response. The procedure in the HLR is then terminated.
No Roaming Number Allocated
The HLR request to the VLR to provide a roaming number may fail for a number of reasons (see
subclause 8.4). If the reason is "Facility Not Supported", the user error is set to "Facility Not Supported";
otherwise, if the reason for failure is anything other than "Absent Subscriber" or "No Roaming Number
Available", the user error is set to "System Failure". The error is returned to the Gateway MSC in the
MAP_SEND_ROUTING_INFORMATION service response. The procedure in the HLR is then terminated.
If the reason for failure is "Absent Subscriber" or "No Roaming Number Available", then the procedure
continues as described in the MS Not Reachable subclause above.