QoS control refers to the authorization and enforcement of the maximum QoS that is authorized for a service data flow, for a QoS Flow or for the PDU Session. A service data flow may be either of IP type or of Ethernet type. PDU Sessions may be of IP type or Ethernet type or unstructured.
The PCF, in a dynamic PCC Rule, associates a service data flow template to an authorized QoS that is provided in a PCC Rule to the SMF. The PCF may also activate a pre-defined PCC Rule that contains that association.
The authorized QoS for a service data flow template shall include a 5QI and the ARP. For a 5QI of GBR or Delay-critical GBR resource type, the authorized QoS shall also include the MBR, GBR and may include the QoS Notification Control parameter (for notifications when authorized GFBR can no longer ( or can again) be fulfilled). For 5QI of Non-GBR resource type, the authorized QoS may include the MBR and the Reflective QoS Control parameter. The 5QI value can be standardized (i.e. referring to QoS characteristics as defined in clause 5.7.3 of TS 23.501), pre-configured (i.e. referring to QoS characteristics configured in the RAN) or dynamically assigned (i.e. referring to QoS characteristics provided by the PCF as Explicitly signalled QoS Characteristics in the PDU Session related policy information described in clause 6.4).
QoS control also refers to the authorization and enforcement of the Session-AMBR and default 5QI/ARP combination. The PCF may provide the Authorized Session-AMBR and the Authorized default 5QI and ARP combination as part of the PDU Session information for the PDU Session to the SMF. The Authorized Session-AMBR and Authorized default 5QI/ARP values takes precedence over other values locally configured or received at the SMF.
In home routed roaming, the H-SMF may provide the QoS constraints received from the VPLMN (defined in clause 22.214.171.124.2 of TS 23.502) to the H-PCF. The H-PCF ensures that the Authorized Session-AMBR value does not exceed the Session-AMBR value provided by the VPLMN and the Authorized default 5QI/ARP contains a 5QI and ARP value supported by the VPLMN. If no QoS constraints are provided the H-PCF considers that no QoS constraints apply unless operator policies define any. The PCF shall also consider the QoS constraints for the setting of the Subsequent Authorized default 5QI/ARP and Subsequent Authorized Session-AMBR.
For policy control, the AF interacts with the PCF and the PCF interacts with the SMF as instructed by the AF. For certain events related to policy control, the AF shall be able to give instructions to the PCF to act on its own, i.e. based on the service information currently available. The following events are subject to instructions from the AF:
The authorization of the service based on incomplete service information;
The immediate authorization of the service;
The gate control (i.e. whether there is a common gate handling per AF session or an individual gate handling per AF session component required);
The forwarding of QoS Flow level information or events (see clause 126.96.36.199).
The UE and the AF shall provide all available flow description information (e.g. source and destination IP address and port numbers and the protocol information) to enable the binding functionality and the generation or selection of the service data flow filter(s) in the PCC rules. The AF may also provide a ToS (IPv4) or TC (IPv6) value that is set by the application as part of the flow description information. The PCF generates a PCC Rule with service data flow filter(s) (either as IP Packet Filter set as defined in clause 188.8.131.52 of TS 23.501 or as Ethernet Packet Filter set as defined in clause 184.108.40.206 of TS 23.501) derived from the flow description information.
If SMF indicates that a PDU session is carried over NR satellite access or satellite backhaul, the PCF may take this information into account for the policy decision, e.g. together with any delay requirements provided by the AF.
When SMF indicates that the dynamic satellite backhaul is used to serve the PDU session, QoS monitoring may be used as described in clause 220.127.116.11.
Service pre-emption priority enables the PCF to resolve conflicts where the activation of all requested active PCC rules for services would result in a cumulative authorized QoS which exceeds the Subscribed Guaranteed bandwidth QoS.
If such a determination can be made, the PCF may resolve the conflict by deactivating those selected PCC rules with lower pre-emption priorities and accepting the higher priority service information from the AF. If such a determination cannot be made, the PCF may reject the service information from the AF.
The termination action indicates the action which the SMF instructs the UPF to perform for all PCC rules of a Charging key for which credit is no longer available. The functional description for termination actions is described in TS 32.255.
The SMF shall revert the termination action related instructions for the UPF for all PCC rules of a Charging key when credit is available again.
Traffic mapping information is signalled to the UE by the SMF in the Packet Filter Sets of QoS rules as defined in TS 23.501.
The network shall ensure that the traffic mapping information signalled to UE reflects the QoS Flow binding of PCC rules, except for those extending the inspection beyond what can be signalled to the UE. The PCC rules may restrict what traffic is allowed compared to what is explicitly signalled to the UE. The PCF may, per service data flow filter, indicate that the SMF is required to explicitly signal the corresponding traffic mapping information to the UE, e.g. for the purpose of IMS precondition handling at the UE. In absence of that indication, it is an SMF decision whether to signal the traffic mapping information that is redundant from a traffic mapping point of view.
For QoS Flow for services with no uplink IP flows, there is no need to provide any UL filter to the UE that effectively disallows any useful packet flows in uplink direction.
The default QoS rule will either contain a Packet Filter Set that allows all UL packets or a Packet Filter Set that is generated from the UL SDF filters (and from the DL SDF filters if they are available) which have an indication to signal corresponding traffic mapping information to the UE.
In the case of interworking with E-UTRAN connected to EPC, the specific aspects of the handling of packet filters at the SMF are described in clause 4.11.1 of TS 23.502.
PDU Sessions for IMS Emergency services are provided by the serving network to support IMS emergency when the serving network is configured to support emergency services. The serving network may be either a PLMN or a SNPN. Emergency services are network services provided through an Emergency DNN and may not require a subscription depending on operator policies and local regulatory requirements. For emergency services, the architecture for the non-roaming case is the only applicable architecture model.
For emergency services, the N36 reference point does not apply. Emergency services are handled locally in the serving network.
For a PDU Session serving an IMS emergency session, the PCF makes authorization and policy decisions that restrict the traffic to emergency destinations, IMS signalling and the traffic to retrieve user location information (in the user plane) for emergency services. A PDU Session serving an IMS emergency session shall not serve any other service and shall not be converted to/from any PDU Session serving other services. The PCF shall determine based on the DNN if a PDU Session concerns an IMS emergency session.
The PCC Rule Authorization function selects QoS parameters that allow prioritization of IMS Emergency sessions. If an IMS Emergency session is prioritized the QoS parameters in the PCC Rule shall contain an ARP value that is reserved for intra-operator use of IMS Emergency services. The PCF does not perform subscription check; instead it utilizes the locally configured operator policies to make authorization and policy decisions.
For an emergency DNN, the PCF does not perform subscription check; instead it utilizes the locally configured operator policies to make authorization and policy decisions.
It shall be possible for the PCF to verify that the IMS service information is associated with a UE IP address belonging to an emergency DNN. If the IMS service information does not contain an emergency related indication and the UE IP address is associated with an emergency DNN, the PCF shall reject the IMS service information provided by the P-CSCF (and thus to trigger the release of the associated IMS session), see TS 23.167.
In addition, the PCF shall provide the PEI and the subscriber identifiers (SUPI, GPSI) (if available), received from the SMF at PDU Session establishment, if so requested by the P-CSCF. The SUPI contains an IMSI or a network-specific identifier in the form of a NAI as defined in clauses 5.9.2 and 18.104.22.168 of TS 23.501. If the PCF removes all PCC Rules with a 5QI other than the default 5QI and the 5QI used for IMS signalling, the SMF shall start a configurable inactivity timer (e.g. to enable PSAP Callback session). When the configured period of time expires the SMF shall terminate the PDU Session serving the IMS Emergency session as defined in TS 23.502. If the SMF receives new PCC rule(s) with a 5QI other than the default 5QI and the 5QI used for IMS signalling for the PDU Session serving the IMS Emergency session, the SMF shall cancel the inactivity timer.
Multimedia Priority Services (MPS) is defined in TS 23.501, TS 23.502 and in TS 23.228, utilising the architecture defined for 5GS.
Subscription data for MPS is provided to PCF through the N36/Nudr. To support MPS service, the PCF shall subscribe to changes in the MPS subscription data for Priority PDU connectivity service. Dynamic invocation for MPS provided from an AF using the Priority indicator over N5/Npcf takes precedence over the MPS subscription.
ARP and/or 5QI may be modified. It shall be possible to override the default Priority Level associated with the standardized 5QI.
For dynamic invocation of MPS service, the PCF shall generate the corresponding PCC rule(s) with the ARP and 5QI parameters as appropriate for the prioritized service, as defined in TS 23.501.
Whenever one or more AF sessions of an MPS service are active within the same PDU Session, the PCF shall ensure that the ARP priority level of the QoS Flow for signalling as well as the QoS Flow associated with the default QoS rule is at least as high as the highest ARP priority level used by any authorized PCC rule belonging to an MPS service. If the ARP pre-emption capability is enabled for any of the authorized PCC rules belonging to an MPS service, the PCF shall also enable the ARP pre-emption capability for the QoS Flow for signalling as well as the QoS Flow associated with the default QoS rule.
In the case of IMS MPS, in addition to the above, the following QoS Flow handling applies:
At reception of the indication from subscription information that the IMS Signalling Priority is set for the PDU Session or at reception of service authorization from the P-CSCF (AF) including an MPS session indication and the service priority level as defined in TS 23.228, the PCF shall (under consideration of the requirement described in clauses 5.16.5 and 5.22.3 in TS 23.501) modify the ARP in all the PCC rules that describe the IMS signalling traffic to the value appropriate for IMS Multimedia Priority Services, if upgrade of the QoS Flow carrying IMS Signalling is required. To modify the ARP of the QoS Flow associated with the default QoS rule the PCF shall modify the Authorized default 5QI/ARP.
When the PCF detects that the P-CSCF (AF) released all the MPS sessions and the IMS Signalling Priority is not set for the PDU Session the PCF shall consider changes of the requirement described in clauses 5.16.5 and 5.22.3 in TS 23.501 and modify the ARP in all PCC rules that describe the IMS signalling traffic to an appropriate value according to PCF decision. The PCC rules bound to the QoS Flow associated with the default QoS rule have to be changed accordingly.
The Priority PDU connectivity service targets the ARP and/or 5QI of the QoS Flows, enabling the prioritization of all traffic on the same QoS Flow.
For non-MPS service, the PCF shall generate the corresponding PCC rule(s) as per normal procedures (i.e. without consideration whether the MPS Priority PDU connectivity service is active or not), and shall upgrade the ARP/5QI values suitable for MPS when the Priority PDU connectivity service is invoked. When the Priority PDU connectivity service is revoked, the PCF shall change the ARP/5QI values modified for the Priority PDU connectivity service to appropriate values according to PCF decision.
The PCF shall, at the activation of the Priority PDU connectivity service:
modify the ARP of PCC rules installed before the activation of the Priority PDU connectivity service to the ARP as appropriate for the Priority PDU connectivity service under consideration of the requirement described in clause 5.16.5 of TS 23.501; and
if modification of the 5QI of the PCC rule(s) is required, modify the 5QI of the PCC rules installed before the activation of the Priority PDU connectivity service to the 5QI as appropriate for this service.
The PCF shall, at the deactivation of the Priority PDU connectivity service modify any 5QI and ARP value to the value according to the PCF policy decision.
For PCC rules modified due to the activation of Priority PDU connectivity service:
modify the ARP to an appropriate value according to PCF decision under consideration of the requirement described in clauses 5.16.5 and 5.22.3 in TS 23.501; and
if modification of the 5QI of PCC rule(s) is required, modify the 5QI to an appropriate value according to PCF decision.
MPS for Data Transport Service enables the prioritization of all traffic on the QoS Flow associated with the default QoS rule and other QoS Flows upon AF request. The QoS modification to the QoS Flow associated with the default QoS rule and other QoS Flows is done based on operator policy and regulatory rules by means of local PCF configuration.
Upon receipt of an MPS for Data Transport Service invocation/revocation request from the UE, the AF or the PCF authorizes the request. If the UE has an MPS subscription, MPS for Data Transport Service is authorized by the AF or the PCF, based on AF decision. If the Service User is using a UE that does not have an MPS subscription, the AF authorizes MPS for Data Transport Service:
In the case that the AF authorizes the MPS for Data Transport Service request, after successful authorization, the AF sends the MPS for Data Transport Service request to the PCF over N5/Npcf for QoS Flow modifications, including an indication that PCF authorization is not needed. In this case, the PCF shall not perform any MPS subscription check for the MPS for Data Transport Service request. The AF also indicates to the PCF whether the request is for invoking or revoking MPS for Data Transport Service.
In the case that the AF does not authorize the MPS for Data Transport Service request, the AF sends the request to the PCF over N5/Npcf for authorization and QoS Flow modifications, including an indication that PCF authorization is needed. In this case, the PCF shall perform an MPS subscription check for the MPS for Data Transport Service request. The AF also indicates whether the request is for invoking or revoking MPS for Data Transport Service. The PCF will inform the AF when the UE does not have an MPS subscription associated with the request.
After successful authorization by either AF or PCF as described above, the PCF shall, at the invocation/revocation of MPS for Data Transport Service, perform the same steps for QoS modifications as described above for the activation/deactivation of the Priority PDU connectivity service.
The PCF shall inform the AF of the success or failure of the MPS for Data Transport Service invocation/revocation request. If the PDU Session is deactivated for other reasons that an AF request, the PCF shall notify the AF by deleting the N5 session context.
For MPS for Data Transport Service, the AF may also request an SDF for priority signalling between the UE and the AF, where the AF includes the Priority indicator over N5/Npcf, in order to enable the PCF to set appropriate QoS values for the QoS Flow.
Redirection of uplink application traffic is an option applicable in SMF or in UPF.
PCF may control redirection by provisioning and modifying dynamic PCC rules over the N7 interface, or activate/deactivate the predefined redirection policies in SMF. The PCF may enable/disable redirection and set a redirect destination for every dynamic PCC rule. Redirect information (redirection enabled/disabled and redirect destination) within a PCC Rule instructs the SMF whether or not to perform redirection towards a specific redirect destination. The redirect destination may be provided as part of the dynamic PCC Rule, or may be preconfigured in the SMF or UPF. A redirect destination provided in a dynamic PCC Rule overrides the redirect destination preconfigured in the SMF or UPF for this PCC Rule.
The P-CSCF (i.e. AF) may indicate to the PCF that media of an AF session may share resources with media belonging to other AF sessions according to TS 23.228. For every media flow, the P-CSCF may indicate that the media flow may share resources in both directions or in one direction only (UL or DL).
The PCF makes authorization and policy decisions for the affected AF sessions individually and generates a PCC rule for every media flow in any AF session.
If the PCF received identical indication(s) for resource sharing for multiple AF sessions, the PCF may request the SMF to realize resource sharing for the corresponding set of PCC rules. The PCF provides a DL and/or UL sharing indication with the same value for those PCC rules that are candidate to share resources according to the direction of resource sharing indicated by the AF.
For each direction, the SMF shall take the highest GBR value from each set of PCC rules related with the same sharing indication for this direction and bound to the same QoS Flow and uses that value as input for calculating the GFBR of the QoS Flow. For each direction, the SMF may take the MBR value of the most demanding PCC rule included in each set of PCC rules related with the same sharing indication for this direction and bound to the same QoS Flow and uses that as input for calculating the MFBR of the QoS Flow.
The AF session termination or modification procedure that removes media flows triggers the removal of the corresponding PCC rules from the SMF. The SMF shall recalculate the GFBR (and MFBR) value of the QoS Flow whenever a set of PCC rules with the same sharing indication changes.
Resource sharing is applied as long as there are at least two active PCC rules with the same sharing indication bound to the same QoS Flow.
Resource sharing for different AF sessions is possible only if the P-CSCF, the PCF and the SMF support it.
Traffic steering control is triggered by the PCF initiated request and consists of steering the detected service data flows matching application detection filters or service data flow filter(s) in PCC Rules. The traffic steering control consists in one of the following:
AF influenced Traffic Steering: diverting (at DNAI(s) provided in PCC rules) traffic matching traffic filters provided by the PCF, as described in clause 5.6.7 of TS 23.501.
N6-LAN Traffic Steering: applying a specific N6 traffic steering policy for the purpose of steering the subscriber's traffic to appropriated N6 service functions deployed by the operator or a 3rd party service provider according to operator policy, or an AF request as described in clause 5.6.16 of TS 23.501.
The PCF uses one or more pieces of information such as network operator's policies, user subscription, user's current RAT, network load status, application identifier, time of day, UE location, DNN, related to the subscriber session and the application traffic, as well as information provided by the AF (if applicable), as input for selecting a traffic steering policy.
In the case of AF influenced service function chaining, the PCF takes the SFC ID provided by the AF into account when generating the traffic steering control information for N6-LAN Traffic Steering in the PCC rule. If there is both a network operator configured policy for N6-LAN Traffic Steering in PCF and an AF-provided SFC ID mapping to traffic steering control information, the PCF decides based on local configuration which one takes precedence.
The PCF controls traffic steering by provisioning and modifying traffic steering control information in PCC rules. Traffic steering control information consists of a traffic description and in the case of N6-LAN Traffic Steering, a reference to a traffic steering policy that is configured in the SMF or, in the case of AF influenced Traffic Steering, per DNAI a reference to a traffic steering policy and/or N6 traffic routing information as well as other parameters described in clause 6.3.1 a reference to a traffic steering policy that is configured in the SMF.
The SMF instructs the UPF to perform necessary actions to enforce the traffic steering policy referenced by the PCF. The actual traffic steering applies at the UPF. For enforcing the traffic steering policy, the UPF may support traffic steering related functions as defined by other standard organizations. The mechanism used for routing the traffic over N6 is out of 3GPP scope.
An AF may indicate to the PCF that a media flow of an AF session is allowed to use the same priority as media flows belonging to other AF sessions (instead of the service priority provided for this media flow). In this case, the AF will provide a priority sharing indicator in addition to the application identifier and the service priority. For MCPTT, the service priority and the priority sharing indicator are defined in TS 23.179. The priority sharing indicator is used to indicate what media flows are allowed to share priority.
The PCF makes authorization and policy decisions for the affected AF sessions individually and generates a PCC rule for every media flow as specified in clause 22.214.171.124. The application identifier and the service priority are used to calculate the ARP priority. The AF may also provide suggested pre-emption capability and vulnerability values per media flow to the PCF. The ARP pre-emption capability and the ARP pre-emption vulnerability are set according to operator policies and regulatory requirements, also taking into consideration the application identifier and suggested values, when provided by the AF. The priority sharing indicator is stored for later use.
For PCC rules with the same 5QI assigned and having an associated priority sharing indicator, the PCF shall try to make authorization and policy decisions taking the priority sharing indicator into account and modify the ARP of these PCC rules as follows, (the original ARP values are stored for later use):
The modified ARP priority is set to the highest of the original priority among all the PCC rules that include the priority sharing indicator;
The modified ARP pre-emption capability is set if any of the original PCC rules have the ARP pre-emption capability set;
The modified ARP pre-emption vulnerability is set if all the original PCC rules have the ARP pre-emption vulnerability set.
If the PCF receives an indication that a PCC rule provisioning or modification failed (due to resource reservation failure) then, the PCF may apply pre-emption and remove active PCC rules from the SMF and then retry the PCC rule provisioning or modification. If the PCF does not apply pre-emption, the AF is notified using existing procedures that the resource reservation for the new media flow failed.
The AF may optionally provide pre-emption control information, including pre-emption capability and vulnerability values, in addition to the priority sharing indicator to the PCF. If so, the PCF shall apply pre-emption and remove active PCC rules according to this information when receiving an indication that a PCC rule provisioning or modification failed. The pre-emption control information indicates:
whether media flows sharing priority are candidates to being pre-empted taking into account pre-emption capability and vulnerability values;
how to perform pre-emption among multiple potential media flow candidates of same priority: most recently added media flow, least recently added media flow, media flow with highest requested bandwidth in the AF request.
This feature, when activated by the user, prevents traffics via 3GPP access except for 3GPP PS Data Off Exempt Services. The 3GPP PS Data Off Exempt Services are a set of operator services, defined in TS 22.011 and TS 23.221, that are the only allowed services in both downlink and uplink direction when the 3GPP PS Data Off feature has been activated by the user.
When PCF is deployed, it shall be able to configure the list(s) of 3GPP PS Data Off Exempt Services for 3GPP access, and the Policy Control Request Trigger of 3GPP PS Data Off status change used to inform the PCF from SMF about every change of the 3GPP PS Data Off status.
When the PCF is informed about the activation of 3GPP PS Data Off, it shall update the PCC rules in such a way that for 3GPP access only packets for services belonging to the list(s) of 3GPP PS Data Off Exempt Services are forwarded while all other packets are discarded. Packets sent over non-3GPP access are not affected, and in the case of MA PDU Session, this is ensured by the MA PDU Session Control policy, e.g. for packets not belonging to the 3GPP Data Off Exempt Services, PCF provides PCC rule containing Steering Mode "Active-Standby" with active access as non-3GPP access and no standby access for downlink and uplink direction.
When the PCF receives service information from the AF, in addition to what is specified in clause 6.2.1, PCF shall check if the requested service information belongs to the 3GPP PS Data Off Exempt Services. If the requested service belongs to 3GPP PS Data Off Exempt Services or if the service traffic can be sent over non-3GPP access, PCF shall continue as specified in clause 6.2.1. If the requested service doesn't belong to the 3GPP PS Data Off Exempt Services and the PDU Session is established only over 3GPP access, PCF shall reject the service request.
When the PCF is informed about the deactivation of 3GPP PS Data Off, it shall perform policy control decision as specified in clause 6.2.1 and perform PCC rule operations as specified in clause 6.3.2 to make sure that the services are allowed according to user's subscription and operator policy (irrespective of whether they belong to the list(s) of 3GPP PS Data Off Exempt Services).
When PCF is not deployed, predefined PCC rules, can be configured in the SMF, on a per DNN basis, to ensure the following:
when the SMF is informed about activation of 3GPP PS Data Off, the SMF shall update the predefined PCC rule in a way that for 3GPP access only downlink and optionally uplink packets for services belonging to the list(s) of 3GPP PS Data Off Exempt Services are forwarded while all other downlink and uplink packets are discarded. Packets sent over non-3GPP access are not affected, and in the case of MA PDU Session, this is ensured by the MA PDU Session Control policy, e.g. for packets not belonging to the 3GPP Data Off Exempt Services, the SMF applies predefined PCC rule containing Steering Mode "Active-Standby" with active access as non-3GPP access and no standby access for downlink and uplink direction; and
When SMF is informed about deactivation of 3GPP PS Data Off, the SMF ensures in UPF downlink and uplink packets are forwarded according to the operator policy for the subscriber.
When the UE 3GPP PS Data Off status is "active" and a handover from one access-system to another occurs, the PCF or the SMF when PCF is not deployed performs the above operations so that the downlink and optionally uplink traffic for services not belonging to the list(s) of 3GPP PS Data Off Exempt Services is only prevented via the 3GPP access.