03.353GPPImmediate Service Termination (IST)Stage 2TS
4.1 CAMEL implementation
For the Customised Applications for Mobile network Enhanced Logic (CAMEL) implementation of Immediate Service Termination (IST) for a particular subscriber, an "IST" command (in reality, the CAMEL message "ReleaseCall") must be sent by the gsmSCF of the home PLMN to the gsmSSF controlling the call, for all the calls of the subscriber.
Prior to the sending of the IST command, the Mobile Application Part (MAP) command "Cancel Location" should be sent to the VLR at which the subscriber is registered. This will ensure that the subscriber cannot re-commence service at that VLR after the IST command has been executed. See annex B of GSM 02.32.
The compilation of the list of MSCs to which the IST command should be sent is outside the scope of the present document. However, if a PLMN operator wishes to implement IST using CAMEL, the list of MSCs to which the IST command should be sent for a subscriber is the list of MSCs with which the CAMEL server has a relationship for that subscriber. If this data is not available directly from the CAMEL server, it may be obtained using Fraud Information Gathering System (FIGS) or an Fraud Detection System (FDS) (if the HPLMN is using CAMEL for IST then it is likely that it will also be monitoring the subscriber’s activities using FIGS level 2 or 3, which use CAMEL).
4.2 Non-CAMEL implementation