The HPLMN shall control handling of roaming, when a CAMEL subscriber attempts to register in a network not supporting CAMEL without relying on extra functionality in network entities not supporting CAMEL. The HPLMN can decide for each subscriber whether to allow roaming, or deny individual services (e.g. by applying ODB or denying location up-date). If the HPLMN allows roaming, the OSSs are not supported for the roaming subscriber.

If the CAMEL feature is not supported in the IPLMN the following will happen:

• Mobile originating calls:
  Not applicable.
• Mobile terminating calls:
  Mobile terminating OSSs are not supported in the IPLMN if the HPLMN decides to allow the MT call attempt. The HPLMN may also decide to bar the incoming call attempt, or force the routeing interrogation to take place in the HPLMN.

If a CAMEL subscriber attempts to register in a VPLMN which supports CAMEL, the VPLMN shall indicate in the registration request to the HPLMN the phase of CAMEL which the VPLMN supports. If the VPLMN supports only a CAMEL phase which is lower than the one subscribed the HPLMN shall take such action (including denying the registration request or transferring to the VPLMN subscription information appropriate to the CAMEL phase supported in the VPLMN) as may be decided by the HPLMN operator. If a certain service requires a certain CAMEL phase (e.g. MO SMS requires at least CAMEL phase 3) and the VPLMN does not support that CAMEL phase, the HPLMN may decide to deny roaming or allow roaming without that particular CAMEL OSS.

If the served subscriber requests a basic service (call, short message, GPRS attach, GPRS PDP context etc.) which requires the VPLMN to contact the CSE, the VPLMN shall indicate to the CSE which phase of CAMEL has been negotiated between the HPLMN and the VPLMN for this service. If the VPLMN supports a CAMEL phase which is lower than the one subscribed and the CSE determines that as a consequence a service which is provisioned for the subscriber will not operate correctly, the CSE shall take such action (including denying the call request or handling the call using only CAMEL capabilities supported in the VPLMN) as may be decided by the CSE operator.

The IPLMN shall indicate to the HPLMN which phases of CAMEL it supports. The HPLMN may decide to bar the incoming call attempt before contacting the CSE, or force the routeing interrogation to take place in the HPLMN. When the IPLMN contacts the CSE for instructions to handle an MT call, the IPLMN shall indicate to the CSE the phase of CAMEL which has been negotiated between the HPLMN and the IPLMN for this call. If the IPLMN supports a lower CAMEL phase than the one negotiated between the HPLMN and the IPLMN and the CSE determines that as a consequence a service which is provisioned for the subscriber will not operate correctly, the CSE shall take such action (including denying the call request or handling the call using only CAMEL capabilities negotiated between the HPLMN and the IPLMN) as may be decided by the CSE operator.

In principle, CAMEL based services require support of subscription information in the VPLMN and support for certain information flows between service logic (at the CSE) and the VPLMN. Subscription information are exchanged when a subscriber attempts to register in a VPLMN. Information flows are started when the VPLMN initiates contact to the CSE. Those procedures are de-coupled and happen at different points in time. If both procedures are supported sufficiently, services may be offered to a subscriber. The following chapter identifies requirements for a VPLMN to indicate its support of CAMEL Phase 4 features. If a CAMEL subscriber attempts to register in a VPLMN which supports at least one CAMEL Phase 4 CSI or the enhanced CSE interrogation and control of subscription data, the VPLMN indicates in the registration request to the HPLMN the phase of CAMEL which the VPLMN supports (i.e. at least Phase 4). In addition, the VPLMN indicates which CAMEL Phase 4 CSIs or enhanced CSE interrogation and control of subscription it offers. A VPLMN supports a CAMEL Phase 4 CSI if it is capable of initiating contact with the CSE due to that CSI using CAMEL Phase 4 procedures. If the VPLMN does not support all CSIs or the enhanced CSE interrogation and control of subscription data of CAMEL phase 4, the HPLMN shall take such action (including denying the registration request or transferring to the VPLMN subscription information appropriate to the CAMEL Phase 4 CSI offered by the VPLMN) as may be decided by the HPLMN operator. If a certain service requires a certain CAMEL Phase 4 CSI (e.g. MT SMS handling) and the VPLMN does not support that CAMEL Phase 4 CSI, the HPLMN may decide to deny roaming or allow roaming without that particular CAMEL OSS. If the VPLMN initiates contact with the CSE, or acknowledges a CSE initiated contact, the VPLMN indicates the CAMEL Phase 4 functionality offered to the CSE. This functionality should not contradict the capabilities the VPLMN has offered to the HPLMN at the registration time. Examples of functionality which can be offered to the CSE are:

• Creating additional parties in a call;
• Placing an individual call party on hold;
• Mid Call procedure;
• Inclusion of flexible tone injection;
• etc.

If the IPLMN supports at least one CAMEL Phase 4 CSI, it indicates to the HPLMN (e.g. in the request for routeing information) which CAMEL Phase 4 CSIs it supports. If the IPLMN does not support all CSIs of CAMEL phase 4, the HPLMN shall take such action (including barring the incoming call request or transferring to the IPLMN subscription information appropriate to the CAMEL Phase 4 CSI offered in the IPLMN) as may be decided by the HPLMN operator. If a certain service requires a specific CAMEL Phase 4 CSI and the IPLMN does not support that specific CAMEL Phase 4 CSI, the HPLMN may decide to bar the incoming call attempt, or force the routeing interrogation to take place in the HPLMN, or allow the MT call attempt without that particular CAMEL OSS. The same principles for the IPLMN shall apply as defined in chapter 16.6 for the VPLMN.

This subclause defines the interactions between supplementary services and the CAMEL feature. However, it should be noted that the most effective way to control those service interactions is through managing the provisioning of services. Where possible, subscribers provisioned with services using the CAMEL feature shall not be provisioned with services having an adverse interaction with the CAMEL based services. Supplementary services shall be assumed not to have any knowledge of CAMEL based services. In general, call independent supplementary service operations (registration, erasure, activation, deactivation and interrogation) are not modified by CAMEL. The exceptions to this for CAMEL phase 2 and later are the call forwarding services, described in subclause 18.3.

For the registration of call forwarding supplementary services the network shall accept any forwarded to number for a subscriber who is provided with a TIF-CSI. In this case the HPLMN shall treat the forwarded-to number transparently at the time of registration, i.e. it shall not perform validity checks or translate the format of the number. The forwarding PLMN shall treat the forwarded-to number transparently when the call forwarding service is invoked. The CSE may modify the forwarded-to number within the MO CAMEL Service provided for the subscriber when the call forwarding service is invoked. If the forwarding PLMN does not support CAMEL phase 2, the HPLMN shall consider the call forwarding service as not registered if the forwarded-to number is not stored in international format.

A MultiParty call may include one or more call legs subject to CAMEL based services. If a call leg is subject to CAMEL based services the CSE shall be able to instruct the VPLMN of the served subscriber whether to prohibit the inclusion of that leg in a MultiParty call.

When a terminating call with CUG information is received for a CAMEL marked subscriber, if the terminating CAMEL based service attempts to modify the called party number then:

• If the called subscriber subscribes to CUG then the IPLMN shall release the call to the calling party;
• If the called subscriber does not subscribe to CUG then the IPLMN shall continue the call establishment to the modified called party number.

For an MO call, an MF call, or an MT call subject to CAMEL forwarding, with CUG information, the CSE shall be able to instruct the VPLMN/IPLMN to:

• Continue the call establishment with the original CUG information, or
• Use modified CUG information for that call, or
• Remove CUG information from the call (i.e. continue the call as a non-CUG call).

For an MT call which is not subject to CAMEL forwarding, the CSE shall not be able to modify the CUG information for the call. When an MT call with CUG information is received for a CAMEL marked subscriber, if the terminating CAMEL based service attempts to modify the called party number then:

• If the called subscriber subscribes to CUG then the VPLMN shall release the call to the calling party;
• If the called subscriber does not subscribe to CUG then the VPLMN shall continue the call establishment to the destination defined by the modified called party number.

Advice of Charge is not guaranteed to operate correctly for calls subject to CAMEL phase 1 based services. It is recommended that subscribers are not provisioned with Advice of Charge and any CAMEL based service for which there is an adverse interaction. If CAMEL phase 2 or higher is supported and the phase 2 or higher charging function "CSE controlled e-values" is used, the VPLMN shall use the received e-values from the CSE for the purpose of the AoC supplementary service. Once the VPLMN has received e-values from the CSE, only CSE provided e-values are applicable for this call. The e-values shall be sent by the VPLMN to the MS only if the served subscriber is provided with the AoC supplementary service according to TS 22.086. CAMEL phase 3 or higher allows the CSE to modify e-values for MO and MT calls.

One or both legs of an ECT call may be subject to CAMEL based services. If a call leg is subject to CAMEL based services the CSE shall be able to instruct the VPLMN of the served subscriber whether to prohibit the inclusion of that leg in an explicitly transferred call.

When a call is established the CSE shall be able to instruct the VPLMN/IPLMN whether Subscriber A is prohibited from activating a CCBS request if a subsequent "CCBS possible" indication is received from the destination network or the terminating served subscriber is busy.

When an MT call is established the CSE shall be able to instruct the VPLMN of the served subscriber whether to prohibit Call Deflection.

User-to-User Service activation requests and User-to-User Information received in call control messages may be passed to the CSE.