5.6.4.1 General

In order to support selective traffic routing to the DN or to support SSC mode 3 as defined in clause 5.6.9.2.3, the SMF may control the data path of a PDU Session so that the PDU Session may simultaneously correspond to multiple N6 interfaces. The UPF that terminates each of these interfaces is said to support PDU Session Anchor functionality. Each PDU Session Anchor supporting a PDU Session provides a different access to the same DN. Further, the PDU Session Anchor assigned at PDU Session Establishment is associated with the SSC mode of the PDU Session and the additional PDU Session Anchor(s) assigned within the same PDU Session e.g. for selective traffic routing to the DN are independent of the SSC mode of the PDU Session. When a PCC rule including the Application Function influence on traffic routing Enforcement Control information defined in clause 6.3.1 of TS 23.503 [45] is provided to the SMF, the SMF can decide whether to apply traffic routing (by using UL Classifier functionality or IPv6 multi-homing) based on DNAI(s) included in the PCC rule.

NOTE 1: Application Function influence on traffic routing Enforcement Control information can be either determined by the PCF when requested by AF via NEF as described in clause 5.6.7.1 or statically pre-configured in the PCF.

NOTE 2: Selective traffic routing to the DN supports, for example, deployments where some selected traffic is forwarded on an N6 interface to the DN that is "close" to the AN serving the UE.

This may correspond to

• The Usage of UL Classifier functionality for a PDU Session defined in clause 5.6.4.2.
• The Usage of an IPv6 multi-homing for a PDU Session defined in clause 5.6.4.3.

SMF may also take decision to apply traffic routing (by using UL Classifier functionality or IPv6 multi-homing) in EAS Discovery with EASDF procedure described in TS 23.548 [130].