5G (NR) Terminal Supported PDU Sessions (Cont. 2)

In 5G, the PDU session between the UE (terminal) and the DN (Data Network - Internet or enterprise network) involves not only the radio network element gNB, but also functional units such as SMF, UPF, and AMF in the 5GC. The relevant QoS services are defined by 3GPP in TS23.501 as follows:

I. Internet and QoS: Different frames exchanged in Ethernet-type PDU sessions may use different QoS services on the 5GS network. Therefore, the SMF can provide the UPF with a set of Ethernet packet filters and forwarding rules based on the Ethernet frame structure and the UE MAC address. The UPF then detects and forwards Ethernet frames based on the Ethernet packet filter set and forwarding rules received from the SMF. This is defined in more detail in sections 5.7 and 5.8.2 of TS23.501.

II. Data Authorization and Filtering: When the DN authorizes an Ethernet PDU type PDU session as described in section 5.6.6, the DN-AAA server can provide the SMF with a list of allowed MAC addresses for this PDU session as part of the authorization data. This list can contain up to 16 MAC addresses. When the list is provided for the PDU session, the SMF sets up corresponding filtering rules in the UPF acting as the anchor point for that PDU session. If an allowed MAC address list is provided, the UPF will discard any UL traffic whose source address does not contain one of these MAC addresses.

• In the R18 specification version, PDU sessions of the Ethernet PDU session type are limited to SSC mode 1 and SSC mode 2.
• For PDU sessions established using the Ethernet PDU session type, the SMF may need to ensure that all Ethernet MAC addresses used as UE addresses in the PDU session are reported to the PCF, as requested by the PCF. In this case, as defined in section 5.8.2.12, the SMF controls the UPF to report the different MAC addresses used as source addresses of the frames sent by the UE in the PDU session.

III. PCF and MAC Address：In Release 18, is it permitted to perform AF control for each MAC address in a PDU session? 3GPP defines this in TS 23.503[45] clause 6.1.1.2, where:

• The PCF can use the "UE MAC address change" policy control request trigger defined in TS 23.503[45] Table 6.1.3.5-1 to activate or deactivate the reporting of the UE MAC address.
• The SMF can relocate the UPF serving as the PDU session anchor for an Ethernet PDU session according to TS 23.502[3] clause 4.3.5.8. Relocation can be triggered by mobility events (e.g., handover) or independently of UE mobility, for example, for load balancing reasons. Activating the reporting of the UE MAC address is required for relocating the PSA UPF.