6.2.5 LI at SMSF

33.1273GPPLawful Interception (LI) architecture and functionsRelease 18TS

6.2.5.1 Architecture

In the 5GC network, the SMSF provides functionalities to support the SMS over NAS. The SMSF shall have LI capabilities to generate xIRIs when SMS related to the target UE are handled. Extending the generic LI architecture presented in clause 5, figure 6.2-5 below gives a reference point representation of the LI architecture with SMSF as a CP NF providing the IRI-POI functions.

Figure 6.2-5: LI architecture for LI at SMSF

The LICF present in the ADMF receives the warrant from an LEA, derives the intercept information from the warrant and provides the same to the LIPF.

The LIPF present in the ADMF provisions the IRI-POI present in the SMSF and the MDF2 over LI_X1 interfaces. The LIPF may interact with the SIRF (over LI_SI) present in the NRF to discover the SMSFs in the network.

The IRI-POI present in the SMSF detects the target UE’s SMS, generates and delivers the xIRI to the MDF2 over LI_X2. The xIRI will contain the SMS payload. The MDF2 shall support the capability to deliver the IRI messages including the SMS payload as part of the Interception Product to the LEMF over LI_HI2.

National regulations may require that the MDF2 remove information regarded as content from the payload in case of an IRI only warrant.

6.2.5.2 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 SMSF:

– SUPI.

– PEI.

– GPSI.

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.

6.2.5.3 IRI events

The IRI-POI present in the SMSF shall generate xIRI, when it detects the following specific events or information:

– SMS message.

The SMS message xIRI is generated when the IRI-POI present in an SMSF detects that an SMS message for the target UE is handled.

6.2.5.4 Common IRI parameters

The list of xIRI parameters are specified in TS 33.128 [15]. The xIRIs shall include at the minimum the following information:

– Target identity.

– Time stamp.

– Location information.

– SMS message direction (mobile originated, mobile terminated).

– SMS message payload.

6.2.5.5 Specific IRI parameters

The parameters in each xIRI are defined in TS 33.128 [15].

6.2.5.6 Network topologies

The SMSF shall provide the IRI-POI functions in the following network topology cases:

– Non-roaming case.

– Roaming case, in VPLMN.

NOTE: SMS message delivery over non-3GPP access with N3A Entity in the HPLMN is considered a non-roaming case.