Default-Bearer QoS Handling for 4G and WiFi Sessions

The following procedure explains how the SMF handles the modification of authorized default QoS in 4G and WiFi sessions.

  1. The SMF receives SmPolicyUpdateNotify from PCF with changed QCI/5QI in AuthorizedDefaultQoS and/or a different session AMBR value.

  2. The SMF initiates Update Bearer Request towards S-GW for the default bearer.

    1. In the Update Bearer Request, Bearer Context IE is included for the default bearer and the corresponding Bearer QoS is updated with the changed QCI value.

    2. For the 4G session, the extended Protocol Configuration Options (ePCO), if supported, is included in the Update Bearer Request message. The ePCO includes 5G Authorized QoS Flow Information with updated QCI value for the default flow when the interworking (IWF) is enabled for the session. Otherwise, PCO IE is sent with the same details.

    3. For the WiFi session, Additional Protocol Configuration Options (APCO) is included in the Update Bearer Request message. The APCO contains 5G Authorized QoS Flow Information with updated QCI value for the default flow.

  3. The SMF accepts the Update Bearer Response from S-GW.

  4. On the N4 interface, the following changes are done:

    1. New instance of the BearerLvlInfo IE is included with the changed QCI value for default bearer tunnel.

    2. Update PDR is sent for all PDRs which are a part of default flow to reflect the association with the new BearerLvlInfo IE.

    3. FAR associated with all PDRs in the default flow is updated with the new DSCP marking value if the 5QI-DSCP mapping configuration has a different value for the changed 5QI.