4 Reference Architecture and Connectivity Models

23.5483GPP5G System Enhancements for Edge ComputingRelease 17Stage 2TS

4.1 General

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.

5GS supports Edge Hosting Environment (EHE) deployed in the DN beyond the PSA UPF. An EHE may be under the control of either the operator or 3rd parties.

The Edge Computing features defined in this specification are applicable to PLMN(s) and to SNPN(s).

The Local part of the DN in which EHE is deployed may have user plane connectivity with both a centrally deployed PSA and locally deployed PSA of same DNN. Edge Computing enablers as described in clause 5.13 of TS 23.501 [2], e.g. local routing and traffic steering, session and service continuity, AF influenced traffic routing, are leveraged in this specification.

NOTE: In this release of the specification, Edge Computing is only supported in the non-roaming and LBO roaming scenarios, except for mechanisms described in clause 6.6 and clause 6.5.

Edge Computing in the serving network (e.g. for Local Break Out roaming scenario in case of PLMN access) is supported, but for AF guidance to PCF determination of URSP rules, the Serving network (e.g. VPLMN or serving SNPN) has no control on URSP, so cannot influence UE in selecting a specific Edge Computing related DNN and S-NSSAI.

4.2 Reference Architecture for Supporting Edge Computing

The reference architectures for supporting Edge Computing are based on the reference architectures specified in clause 4.2 of TS 23.501 [2]. The following reference architectures for non-roaming and LBO roaming scenarios further depict the relationship between the 5GS and a DN where Edge Application Servers (EASs) are deployed in an EHE.

Figure 4.2-1 depicts 5GS architecture for non-roaming scenario supporting Edge Computing with UL CL/BP.

Figure 4.2-1: 5GS providing access to EAS with UL CL/BP for non-roaming scenario

Figure 4.2-2 depicts 5GS architecture for non-roaming scenario supporting Edge Computing without UL CL/BP.

Figure 4.2-2: 5GS providing access to EAS without UL CL/BP for non-roaming scenario

Figure 4.2-3 depicts 5GS architecture for LBO roaming scenario supporting Edge Computing with UL CL/BP.

Figure 4.2-3: 5GS providing access to EAS with UL CL/BP for LBO roaming scenario

Figure 4.2-4 depicts 5GS architecture for LBO roaming scenario supporting Edge Computing without UL CL/BP.

Figure 4.2-4: 5GS providing access to EAS without UL CL/BP for LBO roaming scenario

NOTE 1: Only some of the 5GS NFs are shown in the above reference architecture figures. In the above figures, the split between the UPF acting as UL CL/BP and the UPF acting as local PSA is illustrative.

NOTE 2: Only the control plane of EASDF is depicted in the figure, the user plane between the EASDF and the UPF (i.e. over which the DNS messages are exchanged) is part of N6. Additionally, the EADSF may have direct connectivity with the local parts of one or more Data Networks.

4.3 Connectivity Models

5GC supports the following connectivity models to enable Edge Computing:

– Distributed Anchor Point: For a PDU Session, the PSA UPF is in a local site, i.e. close to the UE location. The PSA UPF may be changed e.g. due to UE mobility and using SSC mode 2 or 3.

– Session Breakout: A PDU Session has a PSA UPF in a central site (C-PSA UPF) and one or more PSA UPF in the local site (L-PSA UPF). The C-PSA UPF provides the IP Anchor Point when UL Classifier is used. The Edge Computing application traffic is selectively diverted to the L-PSA UPF using UL Classifier or multi-homing Branching Point mechanisms. The L-PSA UPF may be changed due to e.g. UE mobility.

– Multiple PDU Sessions: Edge Computing applications use PDU Session(s) with a PSA UPF(s) in local site(s). The rest of applications use PDU Session(s) with PSA UPF(s) in the central site(s). Any PSA UPF may be changed due to e.g. UE mobility and using SSC mode 3 with multiple PDU Sessions.

URSP rules, for steering the mapping between UE applications and PDU Sessions, can be used for any connectivity model and they are required for the Multiple PDU Sessions model.

These three connectivity models are illustrated in Figure 4.3-1:

Figure 4.3-1: 5GC Connectivity Models for Edge Computing