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Call Forwarding (Busy) for Prepaid Roamers Using CAP Phase-1 Fails with Release Cause (31) (Doc ID 1424163.1)

Last updated on FEBRUARY 03, 2019

Applies to:

Oracle Communications Network Charging and Control - Version: 3.2.0 and later   [Release: 3.2.0 and later ]
Information in this document applies to any platform.


The following message may be observed in /var/adm/messages:

RAP: No Called Number (may be BCD) - sending release
When a CAMEL Phase-1 IDP trigger comes to SLC it sends back a release with cause (31):

This is a direct result of a Call Forward (on busy) from a roaming subscriber. See the scenario below for more detail.


Call Forwarding Busy occurs when the network has determined that a mobile terminating call cannot be delivered to the called subscriber as subscriber is busy with another call. An alternative destination for that call is available. This alternative destination may be a voice mail or another mobile subscriber. For more details regarding call forwarding please look into <note 1267608.1>

TSAN or Temporary Service Access number is used when a subscriber is roaming in mobile network which supports CAMEL Phase-1 roaming. TSAN number is used to initiate CAMEL phase 2 trigger for call coming from CAMEL Phase-1 network. Using TSAN number HPLMN (Home Public Land Mobile Network) is able to support call from VPLMN (Visited Public Land Mobile Network) which has implemented CAMEL phase-1 roaming.
For complete call flow using TSAN please see "Expected call flow" section of this document.


  1. A calls B.
  2. B is roaming in a VPLMN (Visited Public Land Mobile Network) where CAMEL Phase 1 has been implemented.
  3. B has enabled the Call Forward On Busy feature to C.
  4. The call is diverted to C using CAMEL Phase-1. The trigger IDP (Initial Detection Point) initiated by roaming network arrives at the SLC (Service Logic Controller) of the HPLMN (Home Public Land Mobile Network).

Expected Call Flow

The IDP of CAMEL Phase 1 comes to the SLC. It should then send a connect message using the TSAN number. Then the call should continue using  the CAMEL phase 2 protocol and this call flow:

Actual Call Flow

The call is not successful. The SLC sends a release when it receives a CAMEL Phase-1 IDP with call forwarding information.


Configuring the network to allow call forwarding when roaming.


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