Content for  TS 23.214  Word version:  18.0.0

A predefined PCC/ADC rule is configured in the CP function. The traffic detection filters required in the UP function can be configured either in the CP function and provided to the UP function, as service data flow filter(s), or be configured in the UP function, as the application detection filter identified by an application identifier. For the latter case, the application identifier has to be configured in the CP function and the UP function. The traffic steering policy information can be only configured in the UP function, together with traffic steering policy identifier(s), while the CP function has to be configured with the traffic steering policy identifier(s). Policies for traffic handling in the UP function, which are referred by some identifiers corresponding to the parameters of a PCC/ADC rule, can be configured in the UP function. These traffic handling policies are configured as predefined QER(s), FAR(s) and URR(s). When a predefined PCC/ADC rule is activated/deactivated by the PCRF, PGW-C/TDF-C shall decide what information has to be provided to the PGW-U/TDF-U to enforce the rule based on where the traffic detection filters (i.e. service data flow filter(s) or application detection filter), traffic steering policy information and the policies used for the traffic handling in the UP function are configured and where they are enforced:

• If the predefined PCC/ADC rule contains an application identifier for which corresponding application detection filters are configured in the UP function, the PGW-C/TDF-C shall provide a corresponding application identifier to the UP function;
• If the predefined PCC/ADC rule contains traffic steering policy identifier(s), the PGW-C/TDF-C shall provide a corresponding traffic steering policy identifier(s) to the UP function;
• If the predefined PCC/ADC rule contains service data flow filter(s), the PGW-C/TDF-C shall provide them to the PGW-U/TDF-U;
• If the predefined PCC/ADC rule contains some parameters for which corresponding policies for traffic handling in the UP function are configured in the UP function, the PGW-C/TDF-C shall activate those traffic handling policies via their rule ID(s).

The CP function shall maintain the mapping between a PCC/ADC rule received over Gx/Sd and the flow level PDR rule(s) used on Sx.

The application detection filters required in the UP function can be configured either in the CP function and provided to the UP function as the service data flow filter, or be configured in the UP function identified by an application identifier. When receiving a dynamic PCC/ADC rule from the PCRF which contains an application identifier and/or parameters for traffic handling in the UP function:

• if the application detection filter is configured in the PGW-C/TDF-C, the PGW-C/TDF-C shall provide it in the service data flow filter to the UP function, as well as parameters for traffic handling in the UP function received from the dynamic PCC/ADC rule;
• otherwise, the application detection filters is configured in UP function, the PGW-C/TDF-C shall provide to PGW-U/TDF-U with the application identifier and the parameters for traffic handling in the UP function as required based on the dynamic PCC/ADC rule.

The CP function shall maintain the mapping between a PCC/ADC rule received over Gx/Sd and the flow level PDR(s) used on Sx.

The uplink application's traffic redirection may be enforced either in the PGW-C/TDF-C (as specified in 5.4.2 Control of user plane forwarding) or directly in the UP function. The redirect destination may be provided in the dynamic PCC/ADC rule or be preconfigured, either in the CP function or in the UP function. When receiving redirect information (redirection enabled/disabled and redirect destination) within a dynamic PCC/ADC rule or being activated/deactivated by the PCRF for the predefined redirection policies, PGW-C/TDF-C shall decide whether to provide and what information to be provided to the UP function based on where the redirection is enforced and where the redirect destination is acquired/preconfigured. When redirection is enforced in the UP function and the redirect destination is acquired from the dynamic PCC/ACD rule or is configured in the CP function, CP function shall provide the redirect destination to the UP function. When redirection is enforced in the CP function, CP function shall instruct the UP function to forward applicable user plane traffic to the CP function.

PFDF shall provide PFD(s) to the PGW-C/TDF-C on the request of PGW-C/TDF-C (pull mode) or on the request of PFD management from SCEF (push mode), as described in TS 23.203. The PGW-C/TDF-C shall provide the PFD(s) to the PGW-U/TDF-U, on which the Application ID corresponding to the PFD(s) is active. The PGW-C/TDF-C supports the procedures for Gw/Gwn as specified in TS 23.203, for management of PFDs. PFD(s) is cached in the PGW-C/TDF-C, and the PGW-C/TDF-C maintains a caching timer associated to the PFD(s). When the caching timer expires and there's no active PCC/ADC rule that refers to the corresponding application identifier, the PGW-C/TDF-C informs the PGW-U/TDF-U to remove the PFD(s) identified by the application identifier using the PFD management message. When a PDR is provided for an Application ID corresponding to the PFD(s) that are not already provided to the PGW-U/TDF-U, the PGW-C/TDF-C shall provide the PFD(s) to the PGW-U/TDF-U (if there are no PFD(s) cached, the PGW-C/TDF-C retrieves them from the PFDF as specified in TS 23.203). When any update of the PFD(s) is received from PFDF by PGW-C/TDF-C (using "push" or "pull" mode), and there are still active PDRs in PGW-U/TDF-U for the Application ID, the PGW-C/TDF-C shall provision the updated PFD set corresponding to the Application ID to the PGW-U/TDF-U using the PFD management message. When the PGW-U/TDF-U receives the updated PFD(s) from either the same or different PGW-C/TDF-C for the same application identifier, the latest received PFD(s) shall overwrite any existing PFD(s) stored in the UP function. When a PFD is removed/modified and this PFD was used to detect application traffic related to an application identifier in a PDR of an Sx session and the PGW-U/TDF-U has reported the application start as described in clause 6.4.2 to the PGW-C/TDF-C for the application instance corresponding to this PFD, the PGW-U/TDF-U shall report the application stop to the PGW-C/TDF-C for the corresponding application instance identifier if the removed/modified PFD in PGW-U/TDF-U results in that the stop of the application instance is not being able to be detected. If the PFDs are managed by local O&M procedures, PFD retrieval is not used; otherwise, the PFDs retrieved from PFDF override any PFDs pre-configured in the PGW-C/TDF-C. When all the PFDs retrieved from the PFDF for an application identifier are removed, the pre-configured PFDs are used. The PGW-C/TDF-C shall provide either the PFDs retrieved from PFDF or the pre-configured PFDs for an application identifier to the PGW-U/TDF-U as specified in clause 6.5.2.

The selection of the UP function (SGW-U, PGW-U, TDF-U, combined SGW/PGW-U) is performed by its respective CP function (SGW-C, PGW-C, TDF-C, combined SGW/PGW-C). The UP function's capabilities shall be signalled during the initial connection establishment between the CP function and the UP function. The CP function shall be made dynamically aware on the UP function load and relative static capacity for which it has an established Sx session as specified in the clauses below. The exact set of parameters used for the selection mechanism is deployment specific and controlled by the operator configuration, e.g. UE capabilities such as the UE support for dual connectivity with NR, and, the UE's location information may be used for selecting UP function in some deployments while may not be used in other deployments.

For PGW-U selection, the PGW-C shall be able to consider the following parameters:

• the PGW-U's dynamic load, at the node level (the PGW-C may then derive the load at the APN level);
• the PGW-U's relative static capacity (among PGW-Us supporting the same APN);
• the PGW-U location configured in the PGW-C and the UE location information provided by the MME/SGSN in order to select the appropriate PGW-U, e.g. for SIPTO above RAN service;
• the capability of the UP function and the functionality required for the particular UE session: An appropriate UP function can be selected by matching the functionality and features required for an UE (which can be derived from the information received over S11/S4/S5/S8 (e.g. APN, mapped UE Usage Type, UE location information, UE capabilities (e.g. UE support for dual connectivity with NR)) or from the PCRF (e.g. need to perform DPI)) with the capabilities of the UP function so as to fulfil the service for the UE, e.g. if L7 based traffic detection is needed then an UP function supporting corresponding functionality needs to be selected.
• to enable APN-AMBR enforcement, whether a PDN connection already exists for the same UE and APN, in which case the same PGW-U shall be selected;

The criteria for PGW-U selection may include load balancing between PGW-Us. The PGW-C may support the Sx Load Control feature. In order to allow the PGW-C to select a PGW-U according to above parameters:

• the SGW-C shall provide the relevant UE's capabilities when available (e.g. UE support for dual connectivity with NR) over the S5/S8 interface.
• the SGW-C may provide the mapped UE Usage Type over the S5 interface.

For SGW-U selection, the SGW-C shall be able to consider the following parameters:

• the SGW-U location (e.g. SGW Service Area) and the UE location information, provided by the MME/SGSN in order to select a UP function close to the UE's point of attachment;
• the SGW-U's dynamic load;
• the SGW-U's relative static capacity (versus other SGW-Us);
• the capability of the UP function and the functionality required for the particular UE session: An appropriate UP function can be selected by matching the functionalities and features required for an UE (which can be derived from the information received over S11/S4 (e.g. individual CIoT capabilities, UE Usage Type, the APN (for selection of combined SGW/PGW), UE capabilities (e.g. UE support for dual connectivity with NR)) with the capabilities of the UP function so as to fulfil the service requirement for the UE then a UP function supporting corresponding functionality needs to be selected.

The criteria for SGW-U selection may include load balancing between SGW-Us. The SGW-C may support the Sx Load Control feature. In order to allow the SGW-C to select a SGW-U according to the above parameters:

• the MME/SGSN shall provide the location of the UE (i.e. ECGI, eNB or TAI for E-UTRAN, and RAI or RNC-ID for UTRAN), the APN (for selection of a combined SGW/PGW), relevant UE capabilities when available (e.g. UE support for dual connectivity with NR) and may provide the mapped UE Usage Type in the Create Session Request over the S11/S4 interface;

A combined SGW/PGW-C selects the SGW-U and PGW-U as defined respectively in clause 5.12.3 and clause 5.12.4, with the following addition:

• The SGW-C determines that it is a combined SGW/PGW-C entity the same way as in the non-split case;
• The combined SGW/PGW-C may optimize UP function selection by selecting the best couple of SGW-U and PGW-U for the requested APN, among all candidate couples of (SGW-U, PGW-U), instead of selecting independently the SGW-U first and then the PGW-U (which may result in selecting non-co-located SGW-U and PGW-U).