7.8 Non-IP data delivery (NIDD) in 5GS

33.1273GPPLawful Interception (LI) architecture and functionsRelease 18TS

7.8.1 Background

7.8.1.1 General

Functions for NIDD (Non-IP Data Delivery) may be used to handle Mobile Originated (MO) and Mobile Terminated (MT) communication for unstructured data (also referred to as Non-IP). Such delivery to an AF is accomplished by one of the following two mechanisms (see TS 23.501 [2] clause 5.31.5):

– Delivery using NEF.

– Delivery using UPF via a Point-to-Point (PtP) N6 tunnel.

If the subscription includes a "NEF Identity for NIDD" corresponding to the DNN and S-NSSAI information, then the SMF selects that NEF as the anchor of this PDU session, otherwise, the SMF selects a UPF as the anchor of this PDU session. If NEF is used, the NIDD traffic is forwarded by NEF to the AF. If UPF is used, the NIDD traffic is forwarded by UPF to the AF.

NIDD applies to non-roaming and roaming with home-routed roaming architecture.

7.8.1.2 NIDD in non-roaming situation

7.8.1.2.1 Delivery using NEF

Figure 7.8-1 presents the architecture for delivery of NIDD using NEF in non-roaming scenario. NIDD using NEF requires a control plane PDU session. The PDU session is established between UE and NEF via AMF and SMF. The user traffic is exchanged with DoNAS (Data over NAS) between UE and AMF, then over N11 interface between AMF and SMF, then over N29 interface between SMF and NEF and finally over N33 interface between NEF and AF (see TS 23.502 [4] clause 4.25).

Figure 7.8-1: 5GS Architecture for NIDD using NEF

7.8.1.2.2 Delivery using UPF via a PtP N6 tunnel

Figure 7.8-2 shows the architecture for delivery of NIDD using UPF via a PtP N6 tunnel in non-roaming scenario. The user traffic is exchanged with DoNAS between UE and AMF, over N11 interface between AMF and SMF, over N4 interface between SMF and UPF and finally over PtP N6 tunnel between UPF and AF. The tunnel is typically a UDP/IP tunnel.

Figure 7.8-2: 5GS Architecture for NIDD using a PtP N6 tunnel

7.8.1.3 NIDD in roaming situation

7.8.1.3.1 Delivery using NEF

In roaming scenario, the PDU session for NIDD using NEF is established between the UE and NEF via V-AMF, V-SMF and H-SMF. The user traffic is exchanged with DoNAS between UE and AMF, then over N11 interface between AMF and V-SMF, over N16 interface between V-SMF and H-SMF and over N29 interface between SMF and NEF and finally over N33 interface between NEF and AF. Figure 7.8-3 shows the architecture for delivery of NIDD using NEF in roaming situation.

Figure 7.8-3: 5GS Architecture for NIDD using NEF in roaming situation

7.8.1.3.2 Delivery using UPF via a PtP N6 tunnel

In roaming scenario, the user traffic is exchanged with DoNAS between UE and AMF, over N11 interface between AMF and V-SMF, over N4 interface between V-SMF and V-UPF, over N9 between V-UPF and H-UPF and finally over PtP N6 tunnel between H-UPF and AF (figure 7.8-4).

Figure 7.8-4: 5GS Architecture of NIDD using a PtP N6 tunnel in roaming situation

7.8.2 LI for NIDD

7.8.2.1 LI for NIDD using NEF

7.8.2.1.1 General

In non-roaming scenario, only NEF will provide IRI-POI and CC-POI.

In roaming scenario, V-SMF shall provide the IRI-POI and CC-POI functions for the visited network while NEF in the home network provides IRI-POI and CC-POI.

NOTE: Only home-routed mode applies.

LI for NIDD using NEF in the VPLMN is described in clause 7.8.2.1.2. LI for NIDD using NEF in the HPLMN is described in clause 7.9.2.1.

Packet header reporting, non-3GPP access and MA-PDU session are not applicable to NIDD.

7.8.2.1.2 Architecture for NIDD using NEF in the VPLMN

This clause describes the LI for NIDD using NEF in the VPLMN. The access method for the delivery of xCC related to NIDD using NEF is based on duplication of packets without modification of the packets at the V-SMF (in case of roaming) and NEF in the home network. The duplicated packets with additional information in a header are sent to MDF3 via LI_X3 for further delivery to the LEMF via LI_HI3. Figure 7.8-5 gives a reference point representation of the LI architecture with V-SMF as a CP NF and UP NF providing the IRI-POI and CC-POI functions for NIDD using NEF in the visited network.

Figure 7.8-5: LI architecture for NIDD using NEF showing LI at V-SMF

7.8.2.1.3 Target identifiers

The LIPF present in the ADMF provisions the intercept information associated with the following target identities to the IRI-POI present in the V-SMF:

– 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.

7.8.2.1.4 IRI events

The IRI-POI present in the V-SMF handles the same records included in xIRIs for NIDD using NEF as those identified in clause 6.2.3.3:

– PDU session establishment.

– PDU session modification.

– PDU session release.

– Start of interception with established PDU session.

– Unsuccessful procedure.

For NIDD using NEF with or without roaming situation, the IRI-POI present in the H-SMF shall avoid generating xIRIs since NEF always provides the xIRIs for the home network.

7.8.2.2 LI for NIDD using a PtP N6 tunnel

In non-roaming scenario, the SMF will provide an IRI POI while UPF shall include a CC-POI.

In roaming scenario, V-SMF and H-SMF shall provide the IRI-POI and V-UPF and H-UPF shall include the CC-POI function as shown in figure 6.2-4 which also concerns IRI-POI and CC-POI functions for IP-based and Ethernet-based PDU sessions.

NOTE: Only home-routed mode applies.

The LI architecture for SMF/UPF for NIDD using a PtP N6 tunnel is the same as presented in figure 6.2-4.

However, the user plane packets between UE and UPF flow through the SMF as shown in figures 7.8-2 and 7.8-4.

The same xIRIs defined in clause 6.2.3.3. for PDU sessions of IP or Ethernet type and the same xCC are also considered for PDU sessions for NIDD using a PtP N6 tunnel, considering unstructured payload format.