Section: 5.6.7 Application Function influence on traffic routing 5.6.7.1 General
Content: The content of this clause applies to non-roaming and to LBO deployments i.e. to cases where the involved entities (AF, PCF, SMF, UPF) belong to the Serving PLMN or AF belongs to a third party with which the Serving PLMN has an SLA agreement. AF influence on traffic routing may apply in the case of Home Routed deployments with Session Breakout (HR SBO) as defined in TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]. In that case when an AF belonging to the V-PLMN (or with an offloading SLA with the V PLMN) desires to provide Traffic Influence policies it may invoke at the V-NEF the API defined in this clause and provide the information listed in Table 5.6.7-1 below but the corresponding Traffic Influence information is provided directly from V-NEF to V-SMF bypassing the PCF. This is further defined in TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130] clause 6.7.2. and the rest of the clause 5.6.7.1 does not address how information related with AF influence on traffic routing may be provided to the SMF in the case of HR SBO. PCF shall not apply AF requests to influence traffic routing to PDU Sessions established in Home Routed mode. The AF may determine the common EAS/DNAI for the UE set in order to indicate a common EAS or common local part of DN, and provide the common EAS/DNAI to the 5GS. An AF may send requests to influence SMF routing decisions for traffic of PDU Session. The AF requests may influence UPF (re)selection and (I-)SMF (re)selection and allow routing user traffic to a local access to a Data Network (identified by a DNAI). The AF may issue requests on behalf of applications not owned by the PLMN serving the UE. If the operator does not allow an AF to access the network directly, the AF shall use the NEF to interact with the 5GC, as described in clause 6.2.10. The AF may be in charge of the (re)selection or relocation of the applications within the local part of the DN (as defined in TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]). Such functionality is not defined. For this purpose, the AF may request to get notified about events related with PDU Sessions. In the case of AF instance change, the AF may send request of AF relocation information. The AF requests are sent to the PCF via N5 (in the case of requests targeting specific on-going PDU Sessions of individual UE(s), for an AF allowed to interact directly with the 5GC NFs) or via the NEF. The AF requests that target existing or future PDU Sessions of multiple UE(s) or of any UE are sent via the NEF and may target multiple PCF(s), as described in clause 6.3.7.2. The PCF(s) transform(s) the AF requests into policies that apply to PDU Sessions. When the AF has subscribed to UP path management event notifications from SMF(s) (including notifications on how to reach a GPSI over N6), such notifications are sent either directly to the AF or via an NEF (without involving the PCF). For AF interacting with PCF directly or via NEF, the AF requests may contain the information as described in the Table 5.6.7-1: Table 5.6.7-1: Information element contained in AF request For each information element mentioned above in the AF request, the detailed description is as follows: 1) Information to identify the traffic. The traffic can be identified in the AF request by - Either a DNN and possibly slicing information (S-NSSAI) or an AF-Service-Identifier - When the AF provides an AF-Service-Identifier i.e. an identifier of the service on behalf of which the AF is issuing the request, the 5G Core maps this identifier into a target DNN and slicing information (S-NSSAI) - When the NEF processes the AF request the AF-Service-Identifier may be used to authorize the AF request. - An application identifier or traffic filtering information (e.g. IP 5 Tuple). The application identifier refers to an application handling UP traffic and is used by the UPF to detect the traffic of the application. When the AF request is for influencing SMF routing decisions, the information is to identify the traffic to be routed. When the AF request is for subscription to notifications about UP path management events, the information is to identify the traffic that the events relate to. The AF request may include a PLMN ID of the PLMN that the DNN and S-NSSAI belong to, as described in clause 4.3.6.1 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. 2) Information about the N6 traffic routing requirements for traffic identified as defined in 1). This includes: - Information about the N6 traffic routing requirements that is provided per DNAI: for each DNAI, the N6 traffic routing requirements may contain a routing profile ID and/or N6 traffic routing information. - An optional indication of traffic correlation, when the information in 4) identifies a group of UEs. This implies the targeted PDU Sessions should be correlated by a common DNAI in the user plane for the traffic identified in 1). If this indication is provided by the AF, the 5GC should select a common DNAI for the target PDU Sessions from the list of DNAI(s) specified in 3). NOTE 1: The N6 traffic routing requirements are related to the mechanism enabling traffic steering in the local access to the DN. The routing profile ID refers to a pre-agreed policy between the AF and the 5GC. This policy may refer to different steering policy ID(s) sent to SMF and e.g. based on time of the day etc. NOTE 2: The mechanisms enabling traffic steering in the local access to the DN are not defined. 3) Potential locations of applications towards which the traffic routing should apply. The potential location of application is expressed as a list of DNAI(s). If the AF interacts with the PCF via the NEF, the NEF may map the AF-Service-Identifier information to a list of DNAI(s). The DNAI(s) may be used for UPF (re)selection and (I-)SMF (re)selection. When only one DNAI is included, and the Indication of traffic correlation is available, the DNAI is used as common DNAI for UEs identified by AF request. The AF request may include a PLMN ID of the PLMN that the list of DNAI(s) belongs to, as described in clause 4.3.6.1 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. 4) Information on the set of target UE(s). This may correspond to: - Individual UEs (i.e. one or a list of UEs) identified using GPSI, or an IP address/Prefix or a MAC address. - Group(s) of UEs identified by External Group Identifier(s) as defined in TS 23.682[ Architecture enhancements to facilitate communications with packet data networks and applications ]  [36] when the AF interacts via the NEF, or Internal-Group Identifier (see clause 5.9.7) when the AF interacts directly with the PCF. - Any UE accessing the combination of DNN, S-NSSAI and DNAI(s). - External Group ID(s) or any UE can both be complemented with External Subscriber Category(s) for a more granular selection of UEs. NEF may map this to Internal Group ID(s) or a combination of Internal Group ID(s) and Subscriber Category(s), defined in TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45]. NOTE 3: Only NEF is aware of the External Subscriber Category. As a user can be associated with multiple Subscriber Category(s), some values of Subscriber Category(s) can correspond to an SLA between an application provider represented by an AF and the 5GC operator. In the NEF API, the combination of application identifier and External Subscriber Category can also be used to refer to this SLA. When the PDU Session type is IPv4 or IPv6 or IPv4v6, and the AF provides an IP address and/or an IP Prefix, or when the PDU Session type is Ethernet and the AF provides a MAC address, this allows the PCF to identify the PDU Session for which this request applies and the AF request applies only to that specific PDU Session of the UE. In this case, additional information such as the UE identity may also be provided to help the PCF to identify the correct PDU Session. Otherwise, the request targets multiple UE(s) and shall apply to any existing or future PDU Sessions that match the parameters in the AF request. When the AF request targets an individual or a list of UE(s) and GPSI is provided within the AF request, the GPSI is mapped to SUPI according to the subscription information received from UDM. When the AF request targets any UE or a group of UE, the AF request is likely to influence multiple PDU Sessions possibly served by multiple SMFs and PCFs. When the AF request targets a group of UE it provides one or several group identifiers in its request. The group identifiers provided by the AF are mapped to Internal-Group identifiers. Members of the group have Group Identifier(s) in their subscription. The Internal-Group Identifier(s) is(are) stored in UDM, retrieved by SMF from UDM and passed by SMF to PCF at PDU Session set-up. The PCF can then map the AF request with user subscription and determine whether an AF request targeting a Group of users applies to a PDU Session. When External Subscriber Category(s) is provided, the NEF maps External Subscriber Category(s) into Subscriber Category(s), the PCF can map the AF request with user subscription and then creates PCC rules for UEs that have the Subscriber Category(s) in their subscription. When the AF request is for influencing SMF routing decisions, the information is to identify UE(s) whose traffic is to be routed. When the AF request is for subscription to notifications about UP path management events, the information is to identify UE(s) whose traffic the events relate to. When the AF request is for traffic forwarding in a PDU Session serving for TSC, the MAC address used by the PDU Session is determined by the AF to identify UE whose traffic is to be routed according to the previously stored binding relationship of the 5GS Bridge and the port number of the traffic forwarding information received from TSN network. 5) Indication of application relocation possibility. This indicates whether an application can be relocated once a location of the application is selected by the 5GC. If application relocation is not possible, the 5GC shall ensure that for the traffic related with an application, no DNAI change takes place once selected for this application. 6) Temporal validity condition. This is provided in the form of time interval(s) or duration(s) during which the AF request is to be applied. When the AF request is for influencing SMF routing decisions, the temporal validity condition indicates when the traffic routing is to apply. When the AF request is for subscription to notifications about UP path management events, the temporal validity condition indicates when the notifications are to be generated. 7) Spatial validity condition on the UE(s) location. This is provided in the form of validity area(s). If the AF interacts with the PCF via the NEF, it may provide geographical area (e.g. a civic address or shapes) and the NEF maps the information to areas of validity based on pre-configuration. The PCF in turn determines area(s) of interest based on validity area(s). When the AF request is for influencing SMF routing decisions, the spatial validity condition indicates that the request applies only to the traffic of UE(s) located in the specified location. When the AF request is for subscription to notifications about UP path management events, the spatial validity condition indicates that the subscription applies only to the traffic of UE(s) located in the specified location. 8) Information on AF subscription to corresponding SMF events. The AF may request to be subscribed to change of UP path associated with traffic identified in the bullet 1) above. The AF request contains: - A type of subscription (subscription for Early and/or Late notifications). The AF subscription can be for Early notifications and/or Late notifications. In the case of a subscription for Early notifications, the SMF sends the notifications before the (new) UP path is configured. In the case of a subscription for Late notifications, the SMF sends the notification after the (new) UP path has been configured. - Notification target address for receiving event notification. - Optionally, an indication of "AF acknowledgment to be expected". The indication implies that the AF will provide a response to the notifications of UP path management events to the 5GC. The SMF may, according to this indication, determine to wait for a response from the AF before the SMF configures in the case of early notification, or activates in the case of late notification, the new UP path as described in clause 5.6.7.2. - Optionally, an immediate reporting flag. The immediate reporting flag is included when AF subscribe for candidate DNAI(s) of UE for common EAS/DNAI selection. With this flag, SMF should immediately response AF with the candidate DNAI(s) using Notification of user plane management event as described in clause 4.3.6.3 in TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. The AF subscription can also request to receive information associating the GPSI of the UE with the IP address(es) of the UE and/or with actual N6 traffic routing to be used to reach the UE on the PDU Session; in this case the corresponding information is sent by the SMF regardless of whether a DNAI applies to the PDU Session. 9) An AF transaction identifier referring to the AF request. This allows the AF to update or remove the AF request and to identify corresponding UP path management event notifications. The AF transaction identifier is generated by the AF. When the AF interacts with the PCF via the NEF, the NEF maps the AF transaction identifier to an AF transaction internal identifier, which is generated by the NEF and used within the 5GC to identify the information associated to the AF request. The NEF maintains the mapping between the AF transaction identifier and the AF transaction internal identifier. The relation between the two identifiers is implementation specific. When the AF interacts with the PCF directly, the AF transaction identifier provided by the AF is used as AF transaction internal identifier within the 5GC. 10) Indication of UE IP address preservation. This indicates UE IP address related to the traffic identified in bullet 1) should be preserved. If this indication is provided by the AF, the 5GC should preserve the UE IP address by preventing reselection of PSA UPF for the identified traffic once the PSA UPF is selected. 11) Information for EAS IP Replacement in 5GC. This indicates the Source EAS identifier and Target EAS identifier (i.e. IP addresses and port numbers of the source and target EAS) for a service subject to Edge Computing. 12) User Plane Latency Requirement. This includes AF requirements for User Plane latency. (see clause 6.3.6 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]). 13) Information on AF change. The AF relocation information includes: - AF Identifier: the identifier of the target AF instance. NOTE 4: The AF relocation information is applicable for interaction with NEF only and it is not stored in UDR or transferred to PCF, even for the case AF directly interacts with PCF. 14) Indication for EAS relocation. This indicates the application(s) are to be relocated. 15) Indication for Simultaneous Connectivity over source and target PSA at Edge Relocation (see clause 6.3.4 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]). Indicates that source and target PSA should coexist for some time at PSA relocation, and may influence the establishment of a temporary N9 forwarding tunnel between the source UL CL and target UL CL. It may also provide guidance for the time interval after the described traffic ceases when the connectivity over the source PSA may be removed. 16) Traffic Correlation ID. Identification of a set of UEs subjecting to the AF request and accessing the application identified by the Traffic Description. UEs associated with the same Traffic Correlation ID and accessing the application identified by the Traffic Description should connect to a common EAS or EAS(es) corresponding to a common DNAI. The following attributes may be provided with the Traffic Correlation ID: - EAS Correlation indication. Indicates selecting a common EAS for a set of UEs identified by Traffic Correlation ID and accessing the application identified by the Traffic Description. - Common EAS IP address. IP address of the common EAS to be accessed by the UEs in the set of UEs subject to AF request, for the application identified by the Traffic Description. NOTE 5: In the case of common EAS selection, if Traffic Correlation ID is provided, either EAS Correlation indication or Common EAS will be included in AF request. - FQDN(s). FQDN(s) corresponding to the application to be accessed by a set of UEs. When FQDN(s) is included, it is used for influencing EAS discovery procedure as defined in TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]. - Indication of traffic correlation as described in 2). An AF may send requests to influence SMF routing decisions, for event subscription or for both. The AF may request to be subscribed to notifications about UP path management events, i.e. a UP path change occurs for the PDU Session. The corresponding notification about a UP path change sent by the SMF to the AF may indicate the DNAI and /or the N6 traffic routing information and/or common EAS that has changed as described in clause 4.3.6.3 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. It may include the AF transaction internal identifier, the type of notification (i.e. early notification or late notification), the Identity of the source and/or target DNAI, the IP address/prefix of the UE or the MAC address used by the UE, the GPSI and the N6 traffic routing information related to the 5GC UP. The AF may subscribe for notifications of candidate DNAI(s) for UE if AF selection of common EAS/DNAI for a set of UEs is used. NOTE 6: The change from the UP path status where no DNAI applies to a status where a DNAI applies indicates the activation of this AF request; the change from the UP path status where a DNAI applies to a status where no DNAI applies indicates the de-activation of this AF request. In the case of IP PDU Session Type, the IP address/prefix of the UE together with N6 traffic routing information indicates to the AF how to reach over the User Plane the UE identified by its GPSI. N6 traffic routing information indicates any tunnelling that may be used over N6. The nature of this information depends on the deployment. NOTE 7: N6 traffic routing information can e.g. correspond to the identifier of a VPN or to explicit tunnelling information such as a tunnelling protocol identifier together with a Tunnel identifier. NOTE 8: In the case of Unstructured PDU Session type the nature of the N6 traffic routing information related to the 5GC UP is described in clause 5.6.10.3. In the case of Ethernet PDU Session Type, the MAC address of the UE together with N6 traffic routing information indicates to the AF how to reach over the User Plane the UE identified by its GPSI. The UE MAC address (es) is reported by the UPF as described in clause 5.8.2.12. The N6 traffic routing information can be, e.g. a VLAN ID or the identifier of a VPN or a tunnel identifier at the UPF. When notifications about UP path management events are sent to the AF via the NEF, if required, the NEF maps the UE identify information, e.g. SUPI, to the GPSI and the AF transaction internal identifier to the AF transaction identifier before sending the notifications to the AF. The PCF, based on information received from the AF, operator's policy, optionally service experience analytics per UP path received from NWDAF, etc. authorizes the request received from the AF and determines for each DNAI, a traffic steering policy ID (derived from the routing profile ID provided by the AF) and/or the N6 traffic routing information (as provided by the AF) to be sent to the SMF as part of the PCC rules. The traffic steering policy IDs are configured in the SMF or in the UPF. The traffic steering policy IDs are related to the mechanism enabling traffic steering to the DN. The DNAIs are related to the information considered by the SMF for UPF selection and (I-)SMF (re)selection, e.g. for diverting (locally) some traffic matching traffic filters provided by the PCF. The PCF acknowledges a request targeting an individual PDU Session to the AF or to the NEF. For PDU Session that corresponds to the AF request, the PCF provides the SMF with a PCC rule that is generated based on the AF request, Local routing indication from the PDU Session policy control subscription information and taking into account UE location presence in area of interest (i.e. Presence Reporting Area). The PCC rule contains the information to identify the traffic, information about the DNAI(s) towards which the traffic routing should apply and optionally, an indication of traffic correlation and/or an indication of application relocation possibility and/or indication of UE IP address preservation. The PCC rule also contains per DNAI a traffic steering policy ID and/or N6 traffic routing information, if the N6 traffic routing information is explicitly provided in the AF request. If Traffic Correlation ID is included in the AF request, with EAS Correlation Indication or Common EAS, and FQDN(s) parameters, the Traffic Correlation ID and the EAS Correlation Indication or Common EAS, and FQDN(s) will be included in the PCC rule sent to SMF. The SMF can use the Traffic Correlation ID to determine that the UE belongs to a set of UEs identified by Traffic Correlation ID and a common EAS should be selected for the set of UE for the traffic identified by Traffic Descriptor as described in clause 6.2.3.2.5 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]. If Traffic Correlation ID is included in the AF request, NEF updates the AF influence data in the UDR with the NEF Notification Endpoint to indicate it as responsible of the set of UEs associated with the Traffic correlation ID and to be notified with 5GC determined information as described in clause 6.2.3.2.7 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]. The PCF provides in the PCC rule with information including the NEF Notification Endpoint for the SMF to notify to the NEF with 5GC determined information related to the UE members of the set of UEs identified by traffic correlation ID. If Traffic Correlation ID, and traffic correlation indication and FQDN(s) is included in the AF request, the Traffic Correlation ID and the traffic correlation indication will be included in the PCC rule sent to SMF. The SMF can use the Traffic Correlation ID to determine that the UE belongs to a set of UEs identified by Traffic Correlation ID and the UE needs to connect to EAS(s) corresponding to a common DNAI selected for the set of UE for the traffic identified by Traffic Descriptor, as described in clause 6.2.3.2.6 of TS 23.548[ 5G System Enhancements for Edge Computing; Stage 2 ]  [130]. The PCF may also provide in the PCC rule information to subscribe the AF (or the NEF) to SMF events (UP path changes) corresponding to the AF request in which case it provides the information on AF subscription to corresponding SMF events received in the AF request. This is done by providing policies at PDU Session set-up or by initiating a PDU Session Modification procedure. When initiating a PDU Session set-up or PDU Session Modification procedure, the PCF considers the latest known UE location to determine the PCC rules provided to the SMF. The PCF evaluates the temporal validity condition of the AF request and informs the SMF to activate or deactivate the corresponding PCC rules according to the evaluation result. When policies specific to the PDU Session and policies general to multiple PDU Sessions exist, the PCF gives precedence to the PDU Session specific policies over the general policies. The PCF authorizes the AF request of User Plane Latency Requirements. If the PCF determines that the requirements can't be authorized, the PCF rejects the AF request. The spatial validity condition is resolved at the PCF. In order to do that, the PCF subscribes to the SMF to receive notifications about change of UE location in an area of interest (i.e. Presence Reporting Area). The subscribed area of interest may be the same as spatial validity condition, or may be a subset of the spatial validity condition (e.g. a list of TAs) based on the latest known UE location. When the SMF detects that UE entered the area of interest subscribed by the PCF, the SMF notifies the PCF and the PCF provides to the SMF the PCC rules described above by triggering a PDU Session Modification. When the SMF becomes aware that the UE left the area subscribed by the PCF, the SMF notifies the PCF and the PCF provides updated PCC rules by triggering a PDU Session Modification. SMF notifications to the PCF about UE location in or out of the subscribed area of interest are triggered by UE location change notifications received from the AMF or by UE location information received during a Service Request or Handover procedure. When the PCC rules are activated, the SMF may, based on local policies, take the information in the PCC rules and, optionally, the Service Experience analytics and/or DN Performance analytics per UP path (including UPF and/or DNAI and/or AS instance) as defined in clause 6.4.3 and clause 6.14.3, respectively, of TS 23.288[ Architecture enhancements for 5G System (5GS) to support network data analytics services ]  [86] into account to: - (re)select UP paths (including DNAI(s)) for PDU Sessions. The SMF is responsible for handling the mapping between the UE location (TAI / Cell-Id) and DNAI(s) associated with UPF and applications and the selection of the UPF(s) that serve a PDU Session. This is described in clause 6.3.3. If the PDU Session is of IP type and if Indication of UE IP address preservation is included in the PCC rules, the SMF should preserve the UE IP address, by not reselecting the related PSA UPF once the PSA UPF is selected, for the traffic identified in the PCC rule. If the user plane latency requirement is included in the PCC rules, the SMF chooses the PSA UPF that satisfies the user plane latency requirement. If the PCC rules are related to a 5G VN group served by the SMF and if the PCC rule includes an indication of traffic correlation, the SMF should select a common DNAI for the PDU Sessions of the 5G VN group, see clause 5.29. - configure traffic steering at UPF, including activating mechanisms for traffic multi-homing or enforcement of an UL Classifier (UL CL). Such mechanisms are defined in clause 5.6.4. This may include that the SMF is providing the UPF with packet handling instructions (i.e. PDRs and FARs) for steering traffic to the local access to the DN. The packet handling instructions are generated by the SMF using the traffic steering policy ID and/or the N6 traffic routing information in the PCC rules corresponding to the applied DNAI. In the case of UP path reselection, the SMF may configure the source UPF to forward traffic to the UL CL/BP so that the traffic is steered towards the target UPF. - if Information on AF subscription to corresponding SMF events has been provided in the PCC rule, inform the AF of the (re)selection of the UP path (UP path change). If the information includes an indication of "AF acknowledgment to be expected", the SMF may decide to wait for a response from the AF before it activates the new UP path, as described in clause 5.6.7.2. When an I-SMF is inserted for a PDU Session, the I-SMF insertion, relocation or removal to a PDU session shall be transparent (i.e. not aware) to the PCF and to the AF. The processing of the AF influence on traffic routing is described in clause 5.34 and detailed procedure is described in clause 4.23.6 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3].