3GPP 23.501 v20.2.0 — the document's own text
5.6.9.2.1 SSC Mode 1
Taught in 12. The connection to a data network (The 5G system architecture, in depth), 5. The connection, and what is promised on it (The 5G system architecture, overview).
For a PDU Session of SSC mode 1, the UPF acting as PDU Session Anchor at the establishment of the PDU Session is maintained regardless of the access technology (e.g. Access Type and cells) a UE is successively using to access the network.
In the case of a PDU Session of IPv4 or IPv6 or IPv4v6 type, IP continuity is supported regardless of UE mobility events.
In this Release of the specification, when IPv6 multihoming or UL CL applies to a PDU Session of in SSC mode 1 and the network allocates (based on local policies) additional PDU Session Anchors to such a PDU Session, these additional PDU Session Anchors may be released or allocated and the UE does not expect that the additional IPv6 prefix is maintained during the lifetime of PDU Session.
SSC mode 1 may apply to any PDU Session type and to any access type.
A UE supporting PDU Connectivity shall support SSC mode 1.