Section: 4.2.11 Network Slice Admission Control Function (NSACF) procedures 4.2.11.1 General
Content: The Network Slice Admission Control Function procedures are performed for an S-NSSAI which is subject to Network Slice Admission Control (NSAC) as described in TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. If charging needs to be enabled, the NSACF may act as a NF (CTF) and interact with the CHF to support the Event based charging as defined in TS 32.290[ Telecommunication management; Charging management; 5G system; Services, operations and procedures of charging using Service Based Interface (SBI) ]  [42]. Depending on the NSAC architecture deployed in the network, three options of NSAC procedures are defined: - Option 1: The NSAC procedure for number of UEs or PDU sessions for an S-NSSAI is based on non-Hierarchal NSAC architecture. The corresponding procedures are described in clause 4.2.11.2 and clause 4.2.11.4 respectively. - Option 2: The NSAC procedure for number of UEs or PDU sessions for an S-NSSAI is based on centralized NSAC architecture. The corresponding procedures are described in clause 4.2.11.2 and clause 4.2.11.4 respectively. - Option 3: The NSAC procedure for number of UEs or PDU sessions for an S-NSSAI is based on hierarchical NSAC architecture. The corresponding procedures are described in clause 4.2.11.2a and clause 4.2.11.4a respectively.