5.6.10.3 Support of Unstructured PDU Session type

Different Point-to-Point (PtP) tunnelling techniques may be used to deliver Unstructured PDU Session type data to the destination (e.g. application server) in the Data Network via N6.

Point-to-point tunnelling based on UDP/IP encapsulation as described below may be used. Other techniques may be supported. Regardless of addressing scheme used from the UPF to the DN, the UPF shall be able to map the address used between the UPF and the DN to the PDU Session.

When Point-to-Point tunnelling based on UDP/IPv6 is used, the following considerations apply:

• IPv6 prefix allocation for PDU Sessions are performed locally by the (H-)SMF without involving the UE.
• The UPF(s) acts as a transparent forwarding node for the payload between the UE and the destination in the DN.
• For uplink, the UPF forwards the received Unstructured PDU Session type data to the destination in the data network over the N6 PtP tunnel using UDP/IPv6 encapsulation.
• For downlink, the destination in the data network sends the Unstructured PDU Session type data using UDP/IPv6 encapsulation with the IPv6 address of the PDU Session and the 3GPP defined UDP port for Unstructured PDU Session type data. The UPF acting as PDU Session Anchor decapsulates the received data (i.e. removes the UDP/IPv6 headers) and forwards the data identified by the IPv6 prefix of the PDU Session for delivery to the UE.
• The (H-)SMF performs the IPv6 related operations but the IPv6 prefix is not provided to the UE, i.e. Router Advertisements and DHCPv6 are not performed. The SMF assigns an IPv6 Interface Identifier for the PDU Session. The allocated IPv6 prefix identifies the PDU Session of the UE.
• For AF influence on traffic routing (described in clause 5.6.7), when the N6 PtP tunnelling is used over the DNAI and the AF provides, by value, information about N6 traffic routing requirements in the AF request, the AF provides N6 PtP tunnelling requirements (IPv6 address and UDP port of the tunnel end in the DN) as the N6 traffic routing information associated to the DNAI; when the SMF notifies the AF of UP path management events, it includes the N6 PtP tunnel information related to the UP (the IPv6 address and the 3GPP defined UDP port of the tunnel end at the UPF) as N6 traffic routing information in the notification.

In this Release of the specification there is support for maximum one 5G QoS Flow per PDU Session of Type Unstructured.

In this Release of specification, the PDU Session of Unstructured PDU Session type is restricted to SSC mode 1 and SSC mode 2.

The UE may acquire from the SMF, at PDU Session Establishment, the MTU that the UE shall consider, see clause 5.6.10.4.