5G Core Part 7 — Reflective QoS

Old town, Rothenburg, Germany [© F2022]

Introduction to Reflective QoS

In my last article, I talked about the new 5G QoS feature called the QoS Notification Control (QNC). Beside the QNC, 5G has another new QoS feature called the Reflective QoS (RQoS).

Before we dive into the details of the operations of the RQoS, let us have a quick revision of the 5GS QoS model highlighted in the 5G Core Part 2 — PDU Session Establishment and Call Flow as follows:

5GS QoS Model with SDF Template, QoS Profile and QoS Rule for UPF, gNB and UE respectively

In short, to setup any Default or Dedicated QoS Flows between a 5G UE (e.g., User Equipment such as a 5G smart phone) and a DN, the SMF needs to signal directly and indirectly all the necessary QoS Constructs such as the QFI, 5QI, ARP, Uplink’s (UL) and Downlink’s Packet Filters, GBR and MBR etc.. to all the 5G Network Functions (NFs) along the user path between the UE and the DN for the QoS Flow such as the:

• SDF Template to the UPF directly via the SMF/UPF’s N4 PFCP interface
• QoS Profile to the gNB indirectly via the AMF’s N2 interface
• QoS Rule to the UE indirectly via the AMF and the gNB over the N1 wireless interface