6.6 Support of AF Guidance to PCF Determination of Proper URSP Rules

23.5483GPP5G System Enhancements for Edge ComputingRelease 17Stage 2TS

This clause describes how an Edge Computing related AF may send guidance to PCF determination of proper URSP rules to send to the UE.

NOTE 1: This clause can apply in all deployment models.

An AF related with Edge computing may need to guide PCF determination of proper URSP rules. The guidance sent by the AF may apply to any UE or to a set of UE(s) e.g. identified by a Group Id. The AF may belong to the operator or to a third party.

NOTE 2: Some examples of the delivery of such AF guidance are shown in Annex D.

An AF may deliver such guidance to the PCF via application guidance for URSP rules determination mechanisms defined in clause 4.15.6.10 of TS 23.502 [3]. This mechanism is defined only to deliver the guidance to a PCF of the HPLMN of the UE.

The PCF may use the AF guidance received from different AFs, UE subscription data and local operator policy to determine the URSP rules to send to a UE. If received guidance information is not consistent with UE subscription data, or the local operator policy do not allow the specific S-NSSAI and DNN provided by the AF guidance, the corresponding AF guidance shall not be used to determine URSP rules.

– Application traffic descriptor from the application guidance is used to set the URSP Traffic Descriptor (e.g. Destination FQDNs or a regular expression in the Domain descriptor), and the PCF determines the URSP rules precedence in the URSP rule (defined in TS 23.503 [4] Table 6.6.2.1-2);

NOTE 3: When multiple Edge Computing specific parameters for the same application are received, the PCF decides the traffic matching priority Rule precedence value of the URSP rule (defined in TS 23.503 [4] Table 6.6.2.1-2).

– Route selection parameter from the application guidance is used to set a Route Selection Descriptor as follows:

– DNN and S-NSSAI from the Route selection parameter from the application guidance are used to set the DNN selection, Network Slice selection components in the Route Selection Descriptor of the URSP rule, respectively (defined in TS 23.503 [4] Table 6.6.2.1-3) based on the UE subscription data;

– Route selection precedence from the application guidance is used to set the Route Selection Descriptor Precedence in the Route Selection Descriptor (defined in TS 23.503 [4] Table 6.6.2.1-3);

– The spatial validity condition for the Route selection precedence from the application guidance if any are used to set the Location Criteria in the Route Selection Descriptor of the URSP rule (defined in TS 23.503 [4] Table 6.6.2.1-3).

NOTE 4: Since the Validation Criteria are not required to be checked during the lifetime of the PDU Session, it may be left to UE implementation (e.g. URSP re-evaluation at mobility change) how well spatial validity conditions in URSPs restrict the access to a specific (DNN, S-NSSAI) to certain locations.

URSP rules based on AF guidance should not be set as the URSP rules with the "match all" traffic descriptor.