This Technical Specification specifies the stage 1 description of the Immediate Service Termination (IST) service which provides the means for the HPLMN to terminate all the activities of an HPLMN subscriber in a VPLMN.
The purpose of this network feature is to enable the HPLMN to control the activities of its subscribers, particularly while they are roaming. If the HPLMN decides (based upon information received via Fraud Information Gathering System (FIGS) or other systems) that a roaming subscriber is behaving in a fraudulent or suspicious manner, the HPLMN can terminate all activities of the subscriber, including calls (including transferred and diverted calls) that are in progress.
This procedure can also be used to terminate all the activities of a subscriber when the subscription has ended.
The primary aim is to enable service providers/network operators to use IST to reduce the amount of money that they lose because of roaming fraud.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Vocabulary for 3GPP Specifications".
For the purposes of this specification the following definitions apply:
subscriber activities that must be terminated. These can be call related events (e.g. call set-up, call termination) or the invocation of call related and call independent supplementary services (e.g. Call Hold, Call Waiting, Call Transfer, Call Forwarding, Unstructured Supplementary Service Data (USSD)).
It shall be possible for the Home Public Land Mobile Network (HPLMN) to instruct any PLMN to terminate immediately all the activities of a specified HPLMN subscriber.
Immediate Service Termination (IST) is controlled by the HPLMN and can be triggered by the HPLMN only.
A subscriber shall be specified by the International Mobile Subscriber Identity (IMSI).
For subscribers that are marked as subscribed to a CAMEL-based service, IST shall be possible using Customised Application for Mobile network Enhanced Logic (CAMEL).
IST shall also be possible for subscribers who are not marked as subscribed to any CAMEL-based service (see Annex A).
The HPLMN will normally direct a request for IST for a particular subscriber to the current Visited PLMN (VPLMN) of that subscriber and the PLMN visited by the subscriber immediately prior to visiting the current VPLMN
The VPLMN shall confirm receipt of the IST command.
The VPLMN shall then terminate all activities of that subscriber in the VPLMN including ongoing calls and forwarded, deflected and transferred calls. The call records of calls terminated by the operation of IST shall contain a field indicating that the call terminated because of the operation of IST.
The VPLMN shall then confirm to the HPLMN that all subscriber activities in that VPLMN have been terminated.
If the specified subscriber has no activities in the VPLMN then the VPLMN shall inform the HPLMN of this.
If after sending an IST command to a VPLMN, the HPLMN does not receive a positive acknowledgement from the VPLMN indicating receipt and comprehension of the IST command, the HPLMN should assume that the VPLMN does not support IST.
It is expected that there will be a need for authentication and confidentiality of the communication made between PLMNs.
These issues are for study under other work items within the SMG10 work programme.