3GPP 23.501 v20.2.0 — the document's own text
5.15.11.3.0 General
Taught in 17. One network, many networks (The 5G system architecture, in depth), 18. Being served by somebody else's network (The 5G system architecture, in depth), 6. One network behaving like several (The 5G system architecture, overview).
In the case of roaming, depending on operator's policy, a roaming agreement or an SLA between the VPLMN and the HPLMN, NSAC of roaming UEs is performed by one of the following modes of NSAC admission:
- VPLMN NSAC Admission; or
- VPLMN with HPLMN assistance NSAC Admission; or
- HPLMN NSAC Admission.
The VPLMN (AMF and SMF) identifies the mode to apply from the AMF subscription data at UE registration and from the SMF subscription data at PDU session establishment.
For all the above modes, for NSAC of roaming UEs for maximum number of UEs per network slice and/or maximum number of PDU Sessions per network slice managed by the VPLMN, each S-NSSAI of the HPLMN that is subject to NSAC is mapped to a corresponding S-NSSAI of the VPLMN subject to NSAC.
For both VPLMN NSAC Admission and VPLMN with HPLMN assistance NSAC Admission modes, each configured S-NSSAI that is subject to NSAC and that is mapped from the HPLMN S-NSSAI, the SMF performs NSAC for home routed PDU sessions according to the principles described in clause 5.15.11.2.