B.1 Example of filter criteria for ECT

24.6293GPPExplicit Communication Transfer (ECT) using IP Multimedia (IM) Core Network (CN) subsystemProtocol specificationRelease 18TS

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:

– Method="INVITE".

NOTE 1: The coding of the Initial Filter Criteria is described in 29.228 [7] and 29.229 [7A].

NOTE 2: When the REFER is forwarded 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 is supported, all signalling has to traverse through the AS.

An example of an IFC Trigger Point configuration where the S-CSCF does not invoke the ECT AS for a PSAP callback:

– Method="INVITE" and not Priority header field with a "psap-callback" header field value.

NOTE 3: Not invoking the ECT AS assumes that the ECT invocation request can be handled elsewhere in the network, e.g. in the PSAP itself.

Annex C (informative):
Example charging model