3GPP 24.501 v20.0.0 — the document's own text
6.3.2.1 General
Taught in 6. Getting on the network, and getting a connection through it (CT1 — the group that writes what your phone says, in depth), 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The purpose of the network-requested PDU session modification procedure is to enable the network to modify a PDU session, re-negotiate header compression configuration associated to a PDU session, convey a port management information container, to trigger EAS rediscovery, provide updated DNS server address(es) due to the newly selected local DNS server or the newly selected EASDF, provide updated ECS configuration information, remove joined UE from one or more multicast MBS sessions associated with a PDU session, update ATSSS parameters (e.g. ATSSS rules), update the MBS service area or the security information of multicast MBS session that the UE has joined or to inform about the result of service-level AA procedure or C2 authorization for UAS services.