24.5293GPPProtocol specificationPSTN/ISDN simulation services: Explicit Communication Transfer (ECT)Release 8TISPANTS
This annex provides an example of a filter criterion that triggers SIP requests that are subject to initial filter criteria evaluation.
When the initial request matches the conditions of the next unexecuted IFC rule for the served user which points to the ECT service, the communication is forwarded to the AS.
An example of an Initial Filter Criteria (IFC) Trigger Point configurations under the assumption that the ECT service is a standalone service that can be invoked by a very specific trigger point active at the destination S-CSCF:
NOTE 1: The coding of the Initial Filter Criteria is described in TS 183 033 .
NOTE 2: When the REFER is sent on an existing dialog, no IFC processing will be performed, because this is a subsequent request on an existing dialog. It follows that when this scenario has to be supported, that then all signalling has to traverse through the AS.
Annex C (informative):
Example charging model