3GPP 23.501 v20.2.0 — the document's own text

5.19.6 SMF Overload Control

Taught in 27. Overload, energy, deployment and the rest (The 5G system architecture, in depth).

The SMF shall contain mechanisms for avoiding and handling overload situations. This can include the following measures:

SMF overload control that could result in rejections of NAS requests.

The SMF overload control may be activated by SMF due to congestion situation at SMF e.g. configuration, by a restart or recovery condition of a UPF, or by a partial failure or recovery of a UPF for a particular UPF(s).

Under unusual circumstances, if the SMF has reached overload situation or there is high probability that signalling storm will happen based on received analytics of signalling storm caused by NF(s) abnormal signalling or set of UEs in specific group, slice or priority as described in clause 6.22 of TS 23.288 [86], the SMF activates NAS level congestion control as specified in clause 5.19.7. The SMF may restrict the load that the AMF(s) are generating, if the AMF is configured to enable the overload restriction.