3GPP 24.501 v20.0.0 — the document's own text
6.2.18 Support of redundant PDU sessions
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The 5GSM sublayer may support establishment of redundant PDU sessions (see clause 5.33.2 of 3GPP TS 23.501 [8]).
In order to establish a set of two redundant PDU sessions, a UE can include a PDU session pair ID, an RSN, or both in a PDU SESSION ESTABLISHMENT REQUEST message for each of the two redundant PDU sessions (see clause 6.4.1.2). The UE can set the PDU session pair ID, the RSN, or both according to URSP or UE local configuration (see 3GPP TS 24.526 [19]).
An SMF receiving a PDU session pair ID, an RSN, or both via a PDU SESSION ESTABLISHMENT REQUEST message operates as specified in clause 5.33.2 of 3GPP TS 23.501 [8]. In addition, an SMF can handle two PDU sessions as redundant even if the UE provides neither a PDU session pair ID nor an RSN in a PDU SESSION ESTABLISHMENT REQUEST message for each of the PDU sessions (see clause 5.33.2 of 3GPP TS 23.501 [8]).