3GPP 23.501 v20.2.0 — the document's own text
5.7.1.6 DL traffic
Taught in 14. What the network promises (The 5G system architecture, in depth), 5. The connection, and what is promised on it (The 5G system architecture, overview).
The following characteristics apply for processing of DL traffic:
- UPF maps User Plane traffic to QoS Flows based on the PDRs.
- UPF performs Session-AMBR enforcement as specified in clause 5.7.1.8 and performs counting of packets for charging.
- UPF transmits the PDUs of the PDU Session in a single tunnel between 5GC and (R)AN, the UPF includes the QFI in the encapsulation header. In addition, UPF may include an indication for Reflective QoS activation in the encapsulation header.
- UPF performs transport level packet marking in DL on a per QoS Flow basis (optionally taking into account PDU Set Importance, if applicable). The UPF uses the transport level packet marking value(s) provided by the SMF (as described in clause 5.8.2.7).
- (R)AN maps PDUs from QoS Flows to access-specific resources based on the QFI and the associated 5G QoS profile, also taking into account the N3 tunnel associated with the DL packet.
NOTE: Packet Filters are not used for the mapping of QoS Flows onto access-specific resources in (R)AN.
- If Reflective QoS applies, the UE creates a new derived QoS rule as defined in clause 5.7.5.2.