Reflective QoS is a new concept in 5G NR and is applicable for UpLink traffic of UE.
This is applicable when SMF has not provided with QoS rules.
This is achieved by UE deriving the QoS rules based on received DL traffic.
It is possible to apply Reflective QoS and non-Reflective QOS concurrently within the same PDU session.
UE Derived QoS Rule
The UE derived QoS rule contains following parameters:
> One UL Packet Filter.
> QFI;
> Precedence value
Control of Reflective QoS
> Reflective QoS is controlled on per-packet basis by using the Reflective QoS Indication.
> Reflective QoS is controlled by Reflective QoS timer (RQ Timer), the duration of this timer can be configured to the UE through the signaling PDU session establishment/modification process, if not configured, it is a default value.
> Reflective QoS is controlled by The packet header parameters RQI and QFI of the N3 (and N9) interface.
> When the 5GC needs to use Reflective QoS for the SDF of a specific QoS flow, the SMF should provide the RQA (Reflective QoS Attribute) of the QoS configuration of this QoS flow to the NG-RAN (through the N2 port), if it has not been provided before past.
Source TS 23 501