QoS flow, QFI, and QoS rules

QoS Flows — The Building Blocks

A QoS flow is the finest granularity of QoS differentiation in 5G. Every IP packet within a PDU session is classified into exactly one QoS flow. Each flow is identified by a QoS Flow Identifier, a 6-bit value ranging from 0 to 63 that is unique within a PDU session. The QFI is carried in the GTP-U extension header between the gNB and UPF, telling both nodes exactly how to treat the packet. Every PDU session automatically includes a default non-GBR QoS flow, and additional flows are created on demand as services require them.