Section: 4.3 Session Management procedures 4.3.1 General
Content: Clause 4.3 defines the Session Management related procedures. It refers to clause 4.4 for the N4 interactions. As defined in clause 5.6.3 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2], considering the case of Home Routed PDU Session, the NAS SM information processing by SMF considers following kind of NAS SM information: - Information that both the V-SMF and H-SMF process: indication of the nature of the NAS SM signalling (e.g. PDU Session Establishment Request), PDU Session Type, Session-AMBR, UE addressing information (allocated IPv4 address, interface identifier). - Information that is not visible to the V-SMF, only processed by the H-SMF: SSC mode, Protocol Configuration Options, SM PDU DN Request Container, QoS Rule(s) and QoS Flow level QoS parameters if any for the QoS Flow(s) associated with the QoS rule(s). NOTE 1: "Information that is not visible to the V-SMF" refers to information that the V-SMF is to relay between the UE and the H-SMF (and that it can store in CDR) but that the V-SMF is not assumed to process otherwise. The NAS SM information processing split between V-SMF and H-SMF is transparent to the UE. Both V-SMF and H-SMF process information interpreted by the AMF as the PDU Session ID, the DNN, the S-NSSAI (with values for the Serving PLMN and HPLMN processed by the V-SMF and with a value for the HPLMN processed by the H-SMF). In the case of Home Routed PDU Session the H-SMF provides also the V-SMF with the IPv6 Prefix allocated to the PDU Session. NOTE 2: IPv6 Prefix allocated to the PDU Session is provided to allow the V-SMF fulfilling regulatory requirements for data storage in the visited country. In non roaming and LBO cases the SMF processes all NAS SM information. In HR roaming scenarios, in order to support SM features only requiring support from the H-SMF without impacting the V-SMF, as specified in detail in TS 29.502[ 5G System; Session Management Services; Stage 3 ]  [36]: - The V-SMF transfers NAS SM information, which is not visible to the V-SMF, in a container towards the H-SMF; - The V-SMF transfers NAS SM information which it does not comprehend (unknown IEs or IEs with an unknown value not set to "reserved" according to the release to which the V-SMF complies), in a different container towards the H-SMF; - The H-SMF transfers NAS SM information which the V-SMF does not need to interpret, in one container towards the V-SMF; - The V-SMF appends unknown NAS SM information received in the N16 container at the end of the NAS SM message it sends to the UE.