School of Specs 23.501v20.2.0

3GPP 23.501 v20.2.0 — the document's own text

6.2.3 UPF

Taught in 4. What each network function does (The 5G system architecture, in depth), 18. Being served by somebody else's network (The 5G system architecture, in depth), 2. Who does what in the core (The 5G system architecture, overview), 2. The pieces a 5G core is made of (The 5G system architecture, quick start).

The User plane function (UPF) includes the following functionality. Some or all of the UPF functionalities may be supported in a single instance of a UPF:

  • Anchor point for Intra-/Inter-RAT mobility (when applicable).
  • Allocation of UE IP address/prefix (if supported) in response to SMF request.
  • External PDU Session point of interconnect to Data Network.
  • Packet routing & forwarding (e.g. support of Uplink classifier to route traffic flows to an instance of a data network, support of Branching point to support multi-homed PDU Session, support of traffic forwarding within a 5G VN group (UPF local switching, via N6, via N19)).
  • Packet inspection (e.g. Application detection based on service data flow template and the optional PFDs received from the SMF in addition, IP or MAC filter-based packet detection functionality).
  • User Plane part of policy rule enforcement, e.g. Gating, Redirection, Traffic steering).
  • Lawful intercept (UP collection).
  • Traffic usage reporting.
  • QoS handling for user plane, e.g. UL/DL rate enforcement, Reflective QoS marking in DL.
  • Uplink Traffic verification (SDF to QoS Flow mapping).
  • Transport level packet marking in the uplink and downlink.
  • Downlink packet buffering and downlink data notification triggering.
  • Sending and forwarding of one or more "end marker" to the source NG-RAN node.
  • Functionality to respond to Address Resolution Protocol (ARP) requests and / or IPv6 Neighbour Solicitation requests based on local cache information for the Ethernet PDUs. The UPF responds to the ARP and / or the IPv6 Neighbour Solicitation Request by providing the MAC address corresponding to the IP address sent in the request.
  • Packet duplication in downlink direction and elimination in uplink direction in GTP-U layer.
  • NW-TT functionality.
  • High latency communication, see clause 5.31.8.
  • ATSSS Steering functionality to steer the MA PDU Session traffic, refer to clause 5.32.6.

NOTE: Not all of the UPF functionalities are required to be supported in an instance of user plane function of a Network Slice.

  • Inter PLMN UP Security (IPUPS) functionality, specified in clause 5.8.2.14.
  • Event exposure, including exposure of network information, i.e. the QoS monitoring information, as specified in clause 5.8.2.18, events as specified in clause 5.2.26.2 of TS 23.502 [3], exposure of data collected for analytics, as specified in clause 5.2.26.2 of TS 23.502 [3] and exposure of the TSC management information as specified in clause 5.8.5.14.
  • Exposure of the UE information, e.g. UE IP address translation information as specified in clause 5.2.26.3 of TS 23.502 [3] and clause 4.15.10 of TS 23.502 [3] if Network address translation (i.e. NAT) functionality of the UE IP address is deployed within UPF.
  • Support of PDU Set based Handling as defined in clause 5.37.5.
  • Support MoQ relay functionality as defined in clause 5.37.9.2.
  • Support connect-UDP client functionality as defined in clauses 5.37.9.3 and 5.37.9.4.
  • NAT information exposure functionality (if NAT is deployed within UPF) as described in clause 5.8.2.17.
  • Features indicated by the means of operator configurable UPF capabilities, as described in clause 5.8.2.21.
  • Handling of Payload Headers as defined in clause 5.8.2.22.
  • Support N6 delay measurement and reporting to SMF, as defined in clause 5.8.2.23.