4 Overview

29.5363GPP5G SystemNetwork Slice Admission Control ServicesRelease 18Stage 3TS

4.1 General

Within the 5GC, the NSACF offers services to the AMF, SMF (or combined SMF+PGW-C), NWDAF and NEF via the Nnsacf service based interface (see 3GPP TS 23.501 [2] and 3GPP TS 23.502 [3]).

Figures 4.1 provides the reference model (in service based interface representation and in reference point representation), with focus on the NSACF and the scope of the present specification.

Figure 4-1: Reference model – NSACF

The functionalities supported by the NSACF are listed in clause 6.2.28 of 3GPP TS 23.501 [2].

The services and service operations provided by the Nnsacf interface are listed in clause 5.2.21 of 3GPP TS 23.502 [3].

When the UE connects to EPS and EPS counting is required, it is the combined SMF+PGW-C invokes NSACF services to perform network slice admission control, during PDN connection establishment procedure and PDN connection release procedure, as specified in clause 5.15.11.5 of 3GPP TS 23.501 [2].

NOTE: A trusted AF can access NSACF services either via NEF to NSACF or directly to NSACF. An untrusted AF shall only be allowed to access NSACF services via NEF. If multiple NSACFs are deployed in the network and the trusted AF is interested in the aggregated report, then the trusted AF collects the report from NEF, instead of contacting multiple NSACFs directly.

4.2 NSAC support in roaming

In the roaming scenario, depending on operator’s policy and roaming agreement, the NSAC procedure may be performed by the VPLMN for roaming UEs (see clause 5.15.11.3 of 3GPP TS 23.501 [2]).

For roaming UEs with LBO PDU session, the vNSACF offers service to the NF in the VPLMN (e.g. AMF in the VPLMN, anchor SMF in the VPLMN). The hNSACF in the HPLMN is not used in this release of the specification (see clause 4.2.4 of 3GPP TS 23.501 [2]).

If the VPLMN is configured to perform NSAC procedure, for roaming UE with HR PDU session, the vNSACF offers service to the NF in VPLMN (e.g. AMF in VPLMN) while the hNSACF offers service to the NF in HPLMN (e.g. anchor SMF in the HPLMN).

If the NSAC service is only provisioned in the HPLMN and the VPLMN supports NSAC procedure towards the HPLMN for roaming UE with HR PDU session, the hNSACF offers service to both NF in VPLMN and NF in HPLMN (e.g. AMF in VPLMN, anchor SMF in HPLMN).