User plane function （UPF） It includes the following functions . stay UPF Some or all of them can be supported in a single instance of UPF function ：
* be used for RAT within / RAT Anchor point of inter mobility （ When applicable ）.
* external PDU Session points for interconnection with data networks .
* Packet routing and forwarding （ for example , An instance that supports uplink classifiers to route traffic to a data network , Support branching points to support multi hosting PDU conversation ）.
* Packet check （ for example , Application process detection based on service data flow template SMF Received optional PFD）.
* Implementation of some policy rules in user plane , For example, gating , redirect , Flow steering ）.
* lawful interception （UP collect ）.
* Traffic usage report .
* User plane QoS handle , for example UL / DL Speed implementation ,DL Reflection in QoS sign .
* Uplink traffic verification （SDF reach QoS Traffic mapping ）.
* Transmission level packet marking in uplink and downlink .
* Downlink packet buffering and downlink data notification triggering .
* One or more “ End tag ” Send and forward to source NG-RAN node .
* as IETF RFC 1027  As specified in ARP Agency and / Or Ethernet PDU Of IETF RFC 4861  Function
IPv6Neighbor Solicitation Proxying. UPF Through the IP Address corresponding MAC Address to respond ARP and / or
IPv6 Neighbor request request .
be careful ： Not all UPF All functions need to be supported in the instance of user plane function of network slice .