In general, the IRI events applicable to S8HR LI are similar to the IRI events defined in clause 7A
except that the LMISF (instead of CSCF) examines and generates the IRI events. However, since the interception in LMISF is used only for S8HR LI (i.e. roaming case), certain events defined in clause 7A
are not applicable:
Any SIP messages sent to, and received from, the target UE as observed at the S-GW/BBIFF shall be delivered as IRI with the additional information as listed in clause 20.3.3
. The LMISF shall include the UE location (along with timestamp) received from the Serving Gateway/BBIFF in the appropriate events.
The provisioned target identity can be a SIP URL, a TEL URL or an IMEI. The method used to verify a target identity is dependent on the call direction. S-GW/BBIFF shall indicate to the LMISF whether the IMS signalling packets were travelling to or from the HPLMN (e.g. based tunnel end point IDs).
For calls originating from the inbound roaming target, calling party identity (e.g. SIP headers: P-Preferred-Id, From) is used verify the target identity. For calls terminating to the inbound roaming target, called party identity (e.g. SIP headers: Request URI, P-Called-Party-Id, To) is used to verify the target.
For incoming calls to an inbound roaming user from a Non-Local-Id as the target, calling party identity (P-Asserted-Id, From) or redirecting party identity (History-Info, Diversion) are used to verify the target. For outgoing calls from an inbound roaming user to a Non-Local-Id as the target, the called party identity (Request-URI, To) is used to verify the target. See Annex I for an informative illustration of Non-Local-Id target interception cases. The LMISF will have to provide the functions provided by the P-CSCF (Annex I) in the VPLMN.
To support the IMEI-based interception, the LMISF shall provide (if possible) the functions equivalent to functions defined for CSCF in clause 7A.8
The mid-call interception is performed using the procedures described in clause 7A.3.1
except that LMISF (instead of CSCF as described in clause 7A.3.1
) maintains the IMS call state, stores the SIP messages and generates the IRI.
When a lawfully authorized interception is deactivated while the target is on an IMS session, the LMISF shall stop delivering the IRI events to the Delivery Function 2.
If compression of the IMS signalling traffic is detected (as defined in RFC 3320  and RFC 4896 ), then the SIP messages are first decompressed (as defined in clause 8 of TS 24.229
) and processed with the steps used to process the uncompressed SIP messages.
The limitations described in the NOTE of clause 15.4.1
apply to lawful interception capabilities provided in the VPLMN for voice services involving the inbound roamers with S8HR as the roaming architecture.