5.13 Support for Edge Computing

Edge computing enables operator and 3rd party services to be hosted close to the UE's access point of attachment, so as to achieve an efficient service delivery through the reduced end-to-end latency and load on the transport network. Edge Computing support by 5GC is specified in this specification and in TS 23.548 [130].

NOTE 1: Edge Computing typically applies to non-roaming and LBO roaming scenarios. For HR roaming scenarios, Edge Computing applies only for "Home Routed with Session Breakout in VPLMN (HR-SBO)" which is described in clause 6.7 of TS 23.548 [130].

The 5G Core Network selects a UPF close to the UE and forwards traffic to enable the local access to the DN via a N6 interface according to the provided traffic steering rules to the UPF. This may be based on the UE's subscription data, UE location, the information from Application Function (AF) as defined in clause 5.6.7, the EAS information reported from EASDF (as defined in TS 23.548 [130]), policy, user plane latency (between the 5G AN and candidate UPF(s)), N6 delay measurement results or other related traffic rules.

NOTE 2: Latencies between 5GC AN and UPF(s) can be configured. If QoS monitoring has previously been performed, the delays of such measurements can also be used.

Due to user or Application Function mobility, the service or session continuity may be required based on the requirements of the service or the 5G network.

The 5G Core Network may expose network information and capabilities to an Edge Computing Application Function.

NOTE 3: Depending on the operator deployment, certain Application Functions can be allowed to interact directly with the Control Plane Network Functions with which they need to interact, while the other Application Functions need to use the external exposure framework via the NEF (see clause 6.2.10 for details).

Edge computing can be supported by one or a combination of the following enablers:

• User plane (re)selection: the 5G Core Network (re)selects UPF to route the user traffic to the local part of the DN as described in clause 6.3.3;
• Local Routing and Traffic Steering: the 5G Core Network selects the traffic to be routed to the applications in the local part of the DN;
• this includes the use of a single PDU Session with multiple PDU Session Anchor(s) (UL CL / IP v6 multi-homing) as described in clause 5.6.4 and the use of a PDU Session with Distributed Anchor Point using SSC mode 2/3.
• Session and service continuity to enable UE and application mobility as described in clause 5.6.9;
• An Application Function may influence UPF (re)selection and traffic routing via PCF or NEF as described in clause 5.6.7;
• Network capability exposure: 5G Core Network and Application Function to provide information to each other via NEF as described in clause 5.20 or directly as described in clause 4.15 of TS 23.502 [3] or from the UPF as described in clause 6.4 of TS 23.548 [130];
• QoS and Charging: PCF provides rules for QoS Control and Charging for the traffic routed to the local part of the DN;
• Support of Local Area Data Network: 5G Core Network provides support to connect to the LADN in a certain area where the applications are deployed as described in clause 5.6.5.
• Discovery and re-discovery of Edge Applications Servers as described in TS 23.548 [130].
• Support of Edge Relocation as described in TS 23.548 [130] and the case of involving AF change as described in clauses 4.3.6.2, 4.3.6.3 and 4.3.6.4 of TS 23.502 [3]. Support of 5GC triggered Edge relocation within the same hosting PLMN's EHEs.
• Support of (I-)SMF (re)selection based on DNAI as described in clauses 4.3.5.1, 4.3.5.2 and 4.23.5.1 of TS 23.502 [3].
• Support of finer sets of UEs.
• Support of common EAS discovery and common DNAI determination for set of UEs as described in clause 6.2 of TS 23.548 [130].
• Support of mapping information between EAS IP/IP range and DNAI as described in clause 6.8 of TS 23.548 [130].
• Support of AF request for DNAI as described in clause 6.8 of TS 23.548 [130].
• Support of Local Offloading Management with I-SMF insertion in Session Breakout connectivity model as described in clause 4.23 of TS 23.502 [3] and in clause 6.10 of TS 23.548 [130].

NOTE 4: Local Offloading Management can be also supported in Distributed Anchor Point and Multiple PDU Sessions connectivity models.

• Support of N6 delay measurement and reporting as described in clause 5.8.2.23. Support of L-PSA UPF (re-)selection and/or an edge relocation considering N6 delay measurement and user plane latency requirement which may trigger an EAS (re-)discovery as described in TS 23.548 [130].