Section: 5.8 User Plane Management 5.8.1 General
Content: User Plane Function(s) handle the user plane path of PDU Sessions. 3GPP specifications support deployments with a single UPF or multiple UPFs for a given PDU Session. UPF selection is performed by SMF. The details of UPF selection is described in clause 6.3.3. The number of UPFs supported for a PDU Session is unrestricted. For an IPv4 type PDU Session or an IPv6 type PDU Session without multi-homing or an IPv4v6 type PDU Session, when multiple PDU Session Anchors are used (due to UL CL being inserted), only one IPv4 address and/or IPv6 prefix is allocated for the PDU Session. For an IPv6 multi-homed PDU Session there are multiple IPv6 prefixes allocated for the PDU Session as described in clause 5.6.4.3. If the SMF had requested the UPF to proxy ARP or IPv6 Neighbour Solicitation for an Ethernet DNN, the UPF should respond to the ARP or IPv6 Neighbour Solicitation Request, itself. Deployments with one single UPF used to serve a PDU Session do not apply to the Home Routed case and may not apply to the cases described in clause 5.6.4. Deployments where a UPF is controlled either by a single SMF or multiple SMFs (for different PDU Sessions) are supported. UPF traffic detection capabilities may be used by the SMF in order to control at least following features of the UPF: - Traffic detection (e.g. classifying traffic of IP type, Ethernet type, or unstructured type) - Traffic reporting (e.g. allowing SMF support for charging). - QoS enforcement (The corresponding requirements are defined in clause 5.7). - Traffic routing (e.g. as defined in clause 5.6.4. for UL CL or IPv6 multi-homing).