3GPP 23.501 v20.2.0 — the document's own text

5.7.6.1 General

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 Packet Filter Set is used in the QoS rule and the PDR to identify one or more packet (IP or Ethernet) flow(s).

NOTE 1: A QoS Flow is characterised by PDR(s) and QoS rule(s) as described in clause 5.7.1.1.

NOTE 2: DL Packet Filter in a Packet Filter Set of a QoS rule may be needed by the UE e.g. for the purpose of IMS precondition.

The Packet Filter Set may contain one or more Packet Filter(s). Every Packet Filter is applicable for the DL direction, the UL direction or both directions.

NOTE 3: The Packet Filter in the Packet Filter Set of the default QoS rule that allows all UL traffic (also known as match-all Packet Filter) is described in TS 24.501 [47].

There are two types of Packet Filter Set, i.e. IP Packet Filter Set and Ethernet Packet Filter Set, corresponding to those PDU Session Types.