D.7.2 UE initiated QoS

When UE is accessing an overlay network via an underlay network as described in clause D.3, if UE-initiated QoS modification in clause 5.30.2.7 and clause 5.30.2.8 is used, the following principles can be considered to enable consistent QoS for User Plane IPsec Child SAs between the two networks:

• UE registers and establishes PDU Session in the overlay network via the User Plane connectivity established in the underlay network. When UE is accessing a specific service of overlay network, a QoS Flow in overlay network can be created according to clause 4.3.3 of TS 23.502 [3]. UE receives the QoS Flow level QoS parameters (e.g. 5QI, GFBR, MFBR, as specified in TS 24.501 [47]) from SMF/PCF in overlay network for the QoS Flow which is created for the specific overlay network service.
• N3IWF in overlay network creates dedicated User Plane IPsec Child SA for each overlay network QoS Flow that requires underlay network QoS support.
• In order to ensure the traffic of the overlay network service is handled with the desired QoS in underlay network, UE can request new QoS Flow for the PDU session in the underlay network, by PDU Session Modification procedure described in clause 4.3.3 of TS 23.502 [3]. The requested QoS can be derived from the QoS Flow level QoS parameters which the UE has received from the overlay network. The Packet Filter in the QoS rule of the request includes overlay network N3IWF IP address and SPI associated with the User Plane IPsec Child SA.
• SMF in the underlay network notifies the PCF that the UE has initiated resource modification, after receiving the PDU Session Modification Request. PCF in the underlay network determines if the request can be authorized based on UE subscription and local policy which can take into account the SLA between overlay network and underlay network. If the request is authorized, PCF generates new PCC rule and installs on SMF in order to create new QoS Flow in underlay network using the QoS Flow level QoS parameters from the overlay network. The PDR/FAR generated refers to the N3IWF IP address and the SPI (provided by the UE in Traffic filter in PDU Session Modification request) to enable filtering and mapping of DL traffic towards the right PDU Session/QoS Flow within the underlay network.
• If SLA exists, it can include a mapping between the DSCP values of the User Plane IPsec Child SAs and the QoS requirement of the overlay network services. The SLA is configured at N3IWF in overlay network and at SMF/PCF in underlay network. N3IWF can provide DSCP value to UE for the User Plane IPsec Child SA at PDU Session Establishment (clause 4.12.5, step 4a and 4c of TS 23.502 [3]). UE can include the DSCP value as an addition in the Packet Filter by initiating the PDU Session Modification procedure in the underlay network. PCF in the underlay network performs QoS authorization of UE QoS request considering the UE subscription and local configuration which takes into account the mapping in the SLA. Details of the mapping between DSCP values of the User Plane IPSec Child SAs and QoS requirement of the overlay network services is described in TS 29.513 [133].