Section: 4.22.2.3.3 QoS Support
Content: The general principles for QoS support with ATSSS as described in clause 5.32.4 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2], apply, with the clarifications provided in this clause. With an MA PDU Session associated to a PDN Connection on EPS there may be separate user-plane tunnels between the AN and the PGW-U+UPF, one associated with 3GPP access in EPC and one associated with non-3GPP access in 5GS. As described in clause 4.11.1.1, the PGW-C+SMF maps the 5G QoS information received from PCC to EPS QoS parameters. This mapping is e.g. based on operator configuration and may result in that multiple QoS flows are mapped to a single EPS bearer. The PGW-C+SMF applies the appropriate QoS signalling in each access, e.g. to manage dedicated bearers in the access associated with EPC and QoS flows in the access associated with 5GC. The PGW-C+SMF also provides N4 rules to UPF for performing QoS enforcement and for mapping downlink traffic to appropriate GTP-U tunnels. As described in clause 5.32.4 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2], for a GBR QoS flow, the QoS profile is provided to a single access network at a given time. GBR QoS flows (and associated MBR, GBR) are thus only enforced in either the access associated to EPC or the access associated to 5GC. In order to maintain consistency between QoS information received via AS and NAS layers in each system, the PGW-C+SMF only provides the GBR QoS information to the UE for the access where the GBR traffic is enforced. The UE shall treat the uplink traffic sent via EPC according to the EPS QoS information received in EPC (e.g. UL TFTs) and the uplink traffic sent via 5GC according to the 5G QoS rules received in 5GS. The UE thus need to determine what access to use (3GPP and Non-3GPP) before applying the uplink QoS treatment. The UPF shall treat the downlink traffic according to the N4 rules (QER, etc.) received from PGW-C+SMF.