09.113GPPSignalling Interworking for supplementary servicesTS
This clause describes the general procedures for the call related and call independent supplementary services version negotiation.
3.1 Call related supplementary services interworking
No interworking identified.
3.2 Call independent supplementary services interworking
On receipt of the REGISTER message from the MS, the MSC/VLR will include the appropriate AC name in the dialogue control portion of the BEGIN message based on the following rules:
– if no version indicator is present, no AC name is included in the BEGIN message towards the HLR (no AC name indicates "version1");
– if the version indicator is less or equal to the highest AC name the MSC/VLR and HLR both support, the "dialogue" will be handled according to the AC name corresponding to the version indicator and to the SS operation received;
– if the version indicator is greater than the highest commonly supported AC name within the network (MSC/VLR, HLR), the "dialogue" will be handled according to this highest AC name if the request from the MS can also be fulfilled with this version of the "dialogue".
The selection of the highest commonly supported AC name by the network is described in GSM 09.02.
It should be noted that unknown parameters of the extension field within the Facility Information Element shall be forwarded to a phase 2 HLR according to the Extensibility rules as defined in GSM 09.02. They may be discarded when sent to a phase 1 HLR.
According to this version of the standards, the highest AC name is "version3".
The description method employed in the clauses 4 to 6 is tabled showing the mapping of parameter values. The exact values of the parameters and parameter tags can be found in the referenced specifications.