7.11 LI at SCEF
33.1273GPPLawful Interception (LI) architecture and functionsRelease 18TS
7.11.1 General
The present document specifies SCEF as POI for:
– NIDD.
– Device triggering.
– MSISDN-less MO SMS.
– Parameter provisioning.
7.11.2 LI for NIDD using SCEF
7.11.2.1 Architecture
The SCEF in the home network and the IWK-SCEF in the visited network shall provide both IRI-POI and CC-POI functions. Figure 7.11-1 gives a reference point representation of the LI architecture with SCEF as a CP NF and UP NF providing the IRI-POI and CC-POI functions for NIDD using SCEF. SCEF is the anchor point for PDN connection establishment and NIDD traffic.
Figure 7.11-1: LI architecture for NIDD using SCEF showing LI at SCEF/IWK-SCEF
7.11.2.2 Target Identities
The LIPF present in the ADMF provisions the intercept information associated with the following target identities to the IRI-POI present in the SCEF:
– IMSI.
– MSISDN.
– External Identifier.
The interception performed on the above three identities are mutually independent, even though, an xIRI may contain the information about the other identities when available.
7.11.2.3 IRI events
The IRI-POI in the SCEF/IWK-SCEF shall generate xIRI when it detects the following specific events or information in both roaming and non-roaming situations:
– PDN connection establishment.
– PDN connection update.
– PDN connection release.
– Start of interception with established PDN connection.
– Unsuccessful procedure.
The PDN connection establishment xIRI is generated when the IRI-POI present in the SCEF/IWK-SCEF detects that a PDN connection for NIDD using SCEF has been established for the target UE. The SCEF plays the role of anchor point for that PDN connection.
The PDN connection update xIRI is generated when the IRI-POI present in the SCEF/IWK-SCEF detects that a PDN connection for NIDD using SCEF is modified for the target UE.
The PDN connection release xIRI is generated when the IRI-POI present in the SCEF/IWK-SCEF detects that a PDN connection for NIDD using SCEF is released for the target UE.
The start of interception with an established PDN connection xIRI is generated when the IRI-POI present in a SCEF/IWK-SCEF detects that interception is activated on the target UE that has an already established PDN connection for NIDD using SCEF in the EPS. When a target UE has multiple PDN connections, this xIRI shall be sent for each PDN connection with a different value of correlation information.
When additional warrants are activated on a target UE, MDF2 shall be able to generate and deliver the start of interception with an established PDN connection related IRI messages to the LEMF associated with the warrants without receiving the corresponding start of interception with an established PDN connection xIRI.
The unsuccessful procedure xIRI is generated when the IRI-POI present in the SCEF/IWK-SCEF detects an unsuccessful procedure for PDN connection establishment, update, release or data delivery, data reception.
SCEF/IWK-SCEF generates xCC for NIDD using SCEF if CC is requested.
7.11.3 LI for device triggering
7.11.3.1 Background
Device triggering is the means by which an SCS/AS sends information to the UE via the SCEF to trigger the UE to perform application specific actions that include initiating communication with the SCS/AS (see TS 23.682 [33] clause 5.2 and TS 29.122 [32] clause 4.4.6).
The device trigger request is authorized by SCEF by submitting the MSISDN or External Identifier of the UE to the HSS. After successful authorization, SCEF forwards the Device trigger request with the IMSI of the UE to the corresponding SMS-SC to be delivered to that UE. The EPS architecture for NIDD is presented in figure 7.11-2.
The device trigger may be recalled or replaced by the SCS/AS if the UE is not reachable at the time the SCS/AS has delivered the device trigger to the UE.
Figure 7.11-2: EPS architecture for device triggering
7.11.3.2 Architecture
The figure 7.11-1 without the CC-POI in SCEF provides the architecture for LI for device triggering.
7.11.3.3 Target identities
The LIPF present in the ADMF provisions the intercept information associated with the following target identities to the IRI-POI present in the SCEF:
– IMSI.
– MSISDN.
– External Identifier.
The interception performed on the above three identities are mutually independent, even though, an xIRI may contain the information about the other identities when available.
7.11.3.4 IRI events
The IRI-POI present in the SCEF shall generate xIRI, when it detects the following specific events or information related to the device triggering service:
– Device trigger.
– Device trigger replacement.
– Device trigger cancellation.
– Device trigger report notification.
The device trigger xIRI is generated when the IRI-POI present in the SCEF detects that a device trigger has been received from an SCS/AS and is delivered to the SMS-SC for the target UE.
The device trigger replacement xIRI is generated when the IRI-POI present in the SCEF detects that a device trigger replacement has been received from an SCS/AS and delivered to the SMS-SC to replace previously submitted device trigger message which is not yet delivered to the target UE.
The device trigger cancellation xIRI is generated when the IRI-POI in the SCEF detects that a device trigger cancellation has been received from an SCS/AS and delivered to the SMS-SC to recall previously submitted device trigger which is not yet delivered to the target UE.
The device trigger report notification xIRI is generated when the IRI-POI present in the SCEF detects that a device trigger report is returned to the SCS/AS with a cause value indicating the trigger delivery outcome (e.g. succeeded, unknown or failed and the reason for the failure).
7.11.4 LI for MSISDN-less MO SMS
7.11.4.1 Background
An MSISDN-less MO SMS is sent by a UE without MSISDN as originator and received by a third party application as destination (i.e. SCS/AS) via SMS-SC and SCEF. MSISDN-less means that the UE has a subscription without MSISDN but an External Identifier which form is username@realm. MSISDN-less MO-SMS service allows MSISDN-less UE to send small data to an SCS/AS using SMS-MO. The SMS-MO received by the SMS-SC through MO submission procedure as defined in TS 23.040 [50], is directly forwarded to the SCEF for further transfer to the recipient SCS/AS (see TS 23.682 [33] clause 5.15).
The SCEF queries the HSS with the IMSI of the UE, obtains the corresponding External Identifier of the UE sending the SMS, and forwards the SMS to the SCS/AS including the External Identifier of the originating UE.
Figure 7.11-3: EPS architecture for MSISDN-less MO SMS
7.11.4.2 Architecture
Figure 7.11-1 without the CC-POI in SCEF provides the architecture for LI for MSISN-less MO SMS.
7.11.4.3 Target identities
The LIPF present in the ADMF provisions the intercept information associated with the following target identities to the IRI-POI present in the SCEF:
– IMSI.
– External Identifier
The interception performed on the above two identities are mutually independent, even though, an xIRI may contain the information about the other identities when available.
7.11.4.4 IRI events
The IRI-POI present in the SCEF shall generate xIRI, when it detects the following specific events or information related to the MSISDN-less MO SMS:
– MSISDN-less MO SMS.
The MSISDN-less MO SMS xIRI is generated when the IRI-POI present in the SCEF detects that a MSISDN-less MO SMS has been received from a target UE by the SCEF and is delivered to the recipient SCS/AS.
7.11.5 LI for parameter provisioning
7.11.5.1 Background
Parameter provisioning is a capability exposed by SCEF to SCS/AS (see TS 23.682 [33] clause 5.10). The SCS/AS can use this capability to tell the network when a device is expected to communicate. The core network can then use this information to create assistance information for the RAN. The RAN may then use the assistance information to minimize UE state transitions. The SCS/AS provides the communication pattern parameters to SCEF, and SCEF updates the UE subscription data via HSS. The parameters shall have a validity time. The validity time indicates when the communication pattern parameters expire. The validity time may be set to indicate that the communication pattern parameters have no expiration time.
Figure 7.11-4: EPS architecture for Parameter Provisioning
7.11.5.2 Architecture
Figure 7.11-1 without the CC-POI in SCEF provides the architecture for LI for parameter provisioning.
7.11.5.3 Target identities
The LIPF present in the ADMF provisions the intercept information associated with the following target identities to the IRI-POI present in the SCEF:
– MSISDN.
– External Identifier.
7.11.5.4 IRI events
The IRI-POI present in the SCEF shall generate xIRI, when it detects the following specific events or information related to Parameter provisioning:
– Communication pattern update.
The communication pattern update xIRI is generated when the IRI-POI present in the SCEF detects that an SCS/AS sent a request to create, update, delete or get communication pattern data related to the targe UE and the SCEF updates or gets these data from the UE subscription profile via HSS.