3GPP 38.300 v19.3.0 — the document's own text

6.5 SDAP Sublayer

Taught in 5. The radio protocol stack, sublayer by sublayer (TSG RAN — the group that specifies the radio, in depth), 2. The six working groups and the line between them (TSG RAN — the group that specifies the radio, overview), 5. The layers a packet falls through, and the three states a device sits in (TSG RAN — the group that specifies the radio, overview).

The main services and functions of SDAP include:

Mapping between a QoS flow and a data radio bearer;

NOTE: When remapping an XR QoS flow carrying PDU sets (see clause 16.15) from one DRB to another (as exemplified in Annex A), all SDAP SDUs belonging to a PDU Set should be mapped to the same DRB.

Marking QoS flow ID (QFI) in both DL and UL packets.

A single protocol entity of SDAP is configured for each individual PDU session.