3GPP 23.501 v20.2.0 — the document's own text
D.1 Introduction
Taught in 24. Networks that are not for everybody (The 5G system architecture, in depth).
This annex provides guidance on how 5GS features and capabilities can be used to support various Non-Public Network deployment options.
Overlay network: When UE is accessing SNPN service via NWu using user plane established in PLMN, SNPN is the overlay network. When UE is accessing PLMN services via NWu using user plane established in SNPN, PLMN is the overlay network.
Underlay network: When UE is accessing SNPN service via NWu using user plane established in PLMN, PLMN is the underlay network. When UE is accessing PLMN services via NWu using user plane established in SNPN, SNPN is the underlay network