QoS Negotiation

The SMF negotiates the QoS with the PCF by initiating a Policy Association Establishment procedure as defined in 3GPP TS 23.502, section 4.16.4. The sessionAMBR and 5gQosProfile parameters that are received from subscription are included in the Npcf_SMPolicyControl_Create request to PCF. The response from PCF may contain the following:

  • Session Rules: A session rule consists of policy information elements that are associated with the PDU session. The QoS related information is Authorized session AMBR and Authorized default QoS.

    • Policy Charging and Control (PCC) Rules: The PCC rule includes the FlowDescription, FlowDirection, and RefQosData parameters among other information. There could be one or more PCC rules in the response from PCF.

      • FlowDescription: This parameter contains packet filters for IP flows. For IP PDU Session Type, the Packet Filter Set supports packet filtering based on at least any combination of:

        - Source / Destination IP address or IPv6 prefix

        - Source / Destination port number

        - Protocol ID of the protocol above IP/Next header type

        - Type of Service (TOS) (IPv4) / Traffic class (IPv6) and mask

        - Flow Label (IPv6)

        - Security parameter index

      • FlowDirection: This parameter indicates the direction of data traffic on which the rule has to be applied. This could be UPLINK, DOWNLINK, or BIDIRECTIONAL.

      • RefQosData: This parameter refers to the QoS description to be applied to this PCC Rule. This matches the QosId of at least one of the QoS Description entries in the response from PCF.

    • QoS Characteristics: The QoS characteristics include parameters such as:

      • Resource Type (GBR, Delay critical GBR, or non-GBR)

      • Priority Level

      • Packet Delay Budget

      • Packet Error Rate

      • Averaging Window

      • Maximum Data Burst Volume (for the Delay-critical GBR resource type only)

        This attribute in the response from PCF is meant to be used only for non-standard 5QI values. For standard 5QI values, the characteristics are already defined in 3GPP TS 23.501, section 5.7.4.

    • QoS Description: The QoS Description parameter consists of the following:

      • 5QI: Standard or non-standard from the QoS Characteristics attribute

      • Uplink and Downlink GBR

      • Uplink and Downlink MBR

      • Maximum Packet Loss Rate

      • QosId – Referenced in PCC rules

      • Default QoS Indication

        There could be more than one QoS Description attribute in the response from PCF.