A.4 3GPP Accesses (GERAN/UTRAN/E-UTRAN) – GTP-based EPC

23.2033GPPPolicy and charging control architectureRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

A.4.0 General

For 3GPP Access (GTP-based), architecture details are described in TS 23.401 [17] and in TS 23.060 [12].

Figure A.1: The 3GPP EPS IP‑CAN (GTP-based)

A.4.1 High Level Requirements

A.4.1.1 Charging related requirements

It shall be possible for the charging system to select the applicable rate based on:

– Location with the granularity as specified for the credit re-authorization trigger Location change in clause A.4.3.1.1;

– User CSG Information, including CSG ID, access mode and CSG membership indication;

– RAT type.

A.4.1.2 QoS control

For 3GPP Access (GTP based) it shall be possible to apply QoS control at APN-level.

QoS control per APN allows the PCC architecture to control the authorized APN-AMBR to be enforced for the total bandwidth usage of non-GBR QCIs at the PCEF within the same APN.

NOTE 1: For the enforcement of the APN-AMBR for all IP‑CAN sessions to the same APN, the IP‑CAN is required to select the same PCEF for all of them.

If there is a QCI assigned to a PCC/QoS rule which is not supported by all RATs of the IP-CAN, the PCRF shall subscribe to the event trigger ‘RAT change’. At inter-RAT mobility, the PCRF will be informed and shall then modify those PCC/QoS rules in the PCEF/BBERF to align their QCI values with those supported by the current RAT.

NOTE 2: It is assumed that the PCRF is configured with the same mapping rules as the MME.

NOTE 3: Subscription to RAT changes ensure that the PCRF is invoked in case the UE moves to a RAT not supporting the assigned QCI in the PCC Rules as well as in case the UE moves back to a RAT supporting the originally assigned QCI. In the latter case, the PCRF can then modify the QCI in the PCC Rules back to the originally assigned value.

It shall be possible for the PCRF to authorize the QCI and ARP of the default EPS bearer to be enforced by the PCEF immediately and/or at a specific point in time by providing the default EPS bearer related policy information as defined in clause A.4.3.4.

A.4.2 Architectural Model and Reference Points

A.4.2.1 Reference architecture

In the 3GPP Access (GTP-based) architecture, see TS 23.401 [17] and in TS 23.060 [12],

– the Policy and Charging Enforcement Function (PCEF) is allocated to the PDN GW;

– the Bearer Binding and Event Reporting Function (BBERF) does not apply.

A.4.3 Functional Description

A.4.3.1 Overall description

A.4.3.1.1 Credit management

For EPS the credit re-authorisation triggers in table A.4.3-1 shall apply in addition to the ones in table 6.1. They are applicable both in case of PCEF and in case of TDF.

Table A.4.3-1: EPS specific credit re-authorization triggers

Credit re-authorization trigger	Description
SGSN change	The UE has moved to a new SGSN. (Note 2)
Serving GW change	The UE has moved to a new Serving GW. (Note 1) (Note 2)
RAT type change.	The characteristics of the air interface, communicated as the radio access type, have changed.
Location change (routeing area)	The routeing area of the UE has changed. (Note 2)
Location change (tracking area)	The tracking area of the UE has changed. (Note 1)
Location change (ECGI)	The ECGI of the UE has changed.(Note 1)
Location change (CGI/SAI)	The CGI/SAI of the UE has changed.(Note 2)
Location change (eNodeB ID)	The eNodeB ID of the UE has changed. (Note 1)
Change of UE presence in Presence Reporting Area	The UE is entering/leaving a Presence Reporting Area
User CSG Information change in CSG cell	User CSG Information has changed when the UE enters/leaves/accesses via a CSG cell
User CSG Information change in subscribed hybrid cell	User CSG Information has changed when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is a CSG member
User CSG Information change in un-subscribed hybrid cell (see NOTE 3 )	User CSG Information has changed when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is not a CSG member
NOTE 1: These triggers are used for E‑UTRAN access. NOTE 2: These triggers are used for GERAN/UTRAN accesses. NOTE 3: Due to the increased signalling load, such reporting should be applied to a limited number of subscribers only.

If the Location change trigger for GERAN/UTRAN or E‑UTRAN is armed, the PDN GW should request the Serving Nodes (then SGSN or MME specifically) to report any changes in location to the level indicated by the trigger according to the procedures described in TS 23.060 [12] or TS 23.401 [17].

The OCS determines at credit management session establishment/modification whether the UE is located in an access type that supports reporting changes of UE presence in Presence Reporting Area. This determination relies on local configuration and may rely on whether the UE is served by a Gn-SGSN (where this reporting is not defined) or by a S4-SGSN. The "SGSN change" trigger and the "Serving GW change" trigger may be used to determine whether the UE is served by a S4-SGSN. If the access type supports it, the OCS may subscribe to Change of UE presence in Presence Reporting Area at any time during the life time of the credit management session.

If the Change of UE Presence in Presence Reporting Area trigger is armed, the PDN GW should request the Serving Nodes (the SGSN or MME) to report any changes in the UE presence in Presence Reporting Area according to the procedures described in TS 23.060 [12] or TS 23.401 [17].

If the User CSG Information change in CSG cell trigger is armed, the PDN GW should request the Serving Nodes (then SGSN or MME specifically) to report any changes in user CSG information when the UE enters/leaves/accesses via a CSG cell.

If the User CSG Information change in subscribed hybrid cell trigger is armed, the PDN GW should request the Serving Nodes (then SGSN or MME specifically) to report any changes in user CSG information when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is a CSG member.

If the User CSG Information change in un-subscribed hybrid cell trigger is armed, the PDN GW should request the Serving Nodes (then SGSN or MME specifically) to report any changes in user CSG information when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is not a CSG member.

If credit re-authorization triggers, event triggers and IP-CAN session related policy information require different levels of reporting of User CSG information for a single IP-CAN session, then the User CSG information to be requested from the Serving Nodes should be changed to the highest level of detail required.

A.4.3.1.2 Event Triggers

For EPS the event triggers in table A.4.3-2 shall apply in addition to the ones in table 6.2 at the PCEF upon the request of the PCRF.

NOTE: The request from the PCRF can be triggered by configured policy, or a request received from the TDF. In case of TDF, this may be a result of credit re-authorization trigger received by the TDF from the OCS.

Table A.4.3-2: EPS specific event triggers

Event trigger	Description	Reported from	Condition for reporting
SGSN change	The UE has moved to a new SGSN. (Note 2)	PCEF	PCRF
Serving GW change	The UE has moved to a new Serving GW. (Note 1) (Note 2)	PCEF	PCRF
RAT type change.	The characteristics of the air interface, communicated as the radio access type, have changed.	PCEF	PCRF
Location change (routeing area)	The routeing area of the UE has changed.	PCEF	PCRF
Location change (tracking area)	The tracking area of the UE has changed. (Note 1)	PCEF	PCRF
Location change (ECGI)	The ECGI of the UE has changed.(Note 1)	PCEF	PCRF
Location change (CGI/SAI)	The CGI/SAI of the UE has changed.(Note 2)	PCEF	PCRF
Location change (eNodeB ID)	The eNodeB ID of the UE has changed. (Note 1)	PCEF	PCRF
Change of UE presence in Presence Reporting Area	The UE is entering/leaving a Presence Reporting Area	PCEF	PCRF
Subscribed APN-AMBR change	The subscribed APN-AMBR has changed	PCEF	Always set
EPS Subscribed QoS change	The QoS of the default EPS bearer has changed.	PCEF	Always set
User CSG Information change in CSG cell	User CSG Information has changed when the UE enters/leaves/accesses via a CSG cell. (Note 3)	PCEF	PCRF
User CSG Information change in subscribed hybrid cell	User CSG Information has changed when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is a CSG member. (Note 3)	PCEF	PCRF
User CSG Information change in un-subscribed hybrid cell (see note)	User CSG Information has changed when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is not a CSG member. (Note 3)	PCEF	PCRF
3GPP PS Data Off status change	The PCEF reports when the 3GPP PS Data Off status changes	PCEF	Always set
NOTE 1: These triggers are used for E‑UTRAN access. NOTE 2: These triggers are used for GERAN/UTRAN accesses. NOTE 3: Due to the increased signalling load, such reporting should be applied to a limited number of subscribers only.

If the Location change trigger is armed, the PDN GW should request the Serving Nodes (then SGSN or MME specifically) to report any changes in location to the level indicated by the trigger according to the procedures described in TS 23.060 [12] or TS 23.401 [17].

The PCRF determines at IP-CAN session establishment/modification whether the UE is located in an access type that supports reporting changes of UE presence in Presence Reporting Area. This determination relies on local configuration and may rely on whether the UE is served by a Gn-SGSN (where this reporting is not defined) or by a S4-SGSN. The "SGSN change" trigger and the "Serving GW change" trigger may be used to determine whether the UE is served by a S4-SGSN. If the access type supports it, the PCRF may subscribe to Change of UE presence in Presence Reporting Area at any time during the life time of the IP-CAN session.

If the Change of UE Presence in Presence Reporting Area trigger is armed, the PDN GW should request the Serving Nodes (SGSN or MME) to report any changes in the UE presence in Presence Reporting Area according to the procedures described in TS 23.060 [12] or TS 23.401 [17].

The User Location Report in the Access Network Information Reporting contains the ECGI and when the bearer is deactivated, information on when the UE was last known to be in that location.

If the User CSG Information change in CSG cell was provided as event trigger, the PDN GW should request the Serving Nodes to report any changes in user CSG information when the UE enters/leaves/accesses via a CSG cell.

If the User CSG Information change in subscribed hybrid cell was provided as event trigger, the PDN GW should request the Serving Nodes to report any changes in user CSG information when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is a CSG member.

If the User CSG Information change in un-subscribed hybrid cell was provided as event trigger, the PDN GW should request the Serving Nodes to report any changes in user CSG information when the UE enters/leaves/accesses via a hybrid cell in which the subscriber is not a CSG member.

A.4.3.1.3 Binding mechanism

As explained in clause 6.1.1, the binding mechanism is performed in three steps: Session Binding, PCC Rule authorization and Bearer Binding.

Session Binding has no 3GPP Access (GTP-based) specifics.

For the authorization of a PCC rule with a GBR QCI the PCRF shall assign a GBR value within the limit supported by the serving network.

NOTE 1: For the authorization of PCC Rules with the same QCI the PCRF may also check that aggregated GBR is within the limits supported by the serving network to minimize the risk of rejection of the bearer by the serving network.

For the 3GPP Access (GTP-based) the Bearer Binding is performed by the PCEF. For GERAN/UTRAN in UE-only mode the Bearer Binding mechanism is restricted by the UE provided binding between a SDF and a bearer for UE initiated resource requests.

A PCEF supporting the Bind to Default Bearer PCC rule attribute shall bind a dynamic PCC rule with this attribute to the default bearer instead of using the bearer binding mechanism defined in clause 6.1.1.4 and keep the binding as long as this attribute remains set. When the PCRF removes the Bind to Default Bearer PCC rule attribute, the bearer binding mechanism as defined in clause 6.1.1.4 shall be applied by using the QoS Class Identifier and ARP values of the dynamic PCC rule. The PCEF support for the Bind to Default Bearer PCC rule attribute is optional, and shall be indicated to the PCRF.

The bearer binding mechanism associates the PCC Rule with the EPS bearer to carry the service data flow. The association shall:

– cause the downlink part of the service data flow to be directed to the EPS bearer in the association; and

– assume that the UE directs the uplink part of the service data flow to the EPS bearer in the association.

Thus, the detection of the uplink part of a service data flow shall be performed on the EPS bearer over which the downlink packets of the same service data flow is directed to.

NOTE 2: For GERAN/UTRAN in UE-only mode the detection of the uplink part of the service data flow may be active, in parallel, on any number of EPS bearers.

When the PDN GW is connected to an SGSN via Gn/Gp (and thus a handover from UTRAN/GERAN to E-UTRAN is possible), the bearer binding in the PCEF shall not combine PCC rules with different ARP values onto the same PDP context. For the UE-only mode (which is based on a UE provided binding) PCC rules with different ARP values shall not be authorized for the same PDP context.

NOTE 3: If Evolved ARP is not supported by the SGSN then this enables a modification of the EPS bearer ARP without impacting the service assignment after a handover to E-UTRAN or after relocation to a S4‑SGSN or a Gn/Gp SGSN that supports Evolved ARP.

A.4.3.1.4 Policy Control

For 3GPP Access (GTP based) the policy control functionalities should include the following functionality for QoS control (in addition to the functionalities listed in clause 6.1.5):

– Authorization and enforcement of the maximum QoS that is authorized for the total bandwidth usage of non-GBR QCIs at an APN.

– Authorization and enforcement of the maximum QoS allocated to the Default EPS bearer. The Default EPS bearer shall have a non-GBR QCI as defined in clause 4.7.2.1 of TS 23.401 [17].

A.4.3.2 Functional Entities

A.4.3.2.1 Policy Control and Charging Rules Function (PCRF)

The following information represents 3GPP EPS specific values of the ones listed in clause 6.2.1.1:

– Subscriber Identifier in the form of IMSI, MSISDN;

– Type of IP‑CAN is set to 3GPP-EPS.

The PCEF may provide the following information (in addition to the information in clause 6.2.1.1):

– Subscribed APN-AMBR;

– Default EPS Bearer QoS.

The SPR may provide the following information for a subscriber (in addition to the information in clause 6.2.1.1) connecting to a specific PDN:

– Authorized APN-AMBR for 3GPP Access;

– Authorized Default EPS Bearer QoS.

The Authorized APN-AMBR and the Authorized Default EPS Bearer QoS are derived by the PCRF from SPR interaction, according to operator policy.

The PCRF shall upon indication of PCC rule removal due to PS to CS handover notify the AF that the associated flows are no longer served by the PS-domain due to PS to CS handover.

If vSRVCC is supported in the serving network, the PCRF (V-PCRF if roaming) provides an indicator via Gx to the PCEF to indicate that vSRVCC is allowed for the flow corresponding to the video component of the voice/video call.

The PCRF shall provide SDF filters in the PCC rule as received in the packet filter information from the PCEF.

If the PCRF receives a request for addition of service data flow(s) with a reference to existing SDF filter identities (and by that to existing PCC rule(s)), the PCRF shall use the QCI or ARP of the existing PCC rule for the new service data flow(s).

NOTE: The reference to existing SDF filter identities informs the PCRF that the request is confined to an existing bearer, having bearer bindings with PCC rules that have the same QCI/ARP combination. Assigning a different QCI or ARP to the new SDFs would cause the procedure to fail, since the PCEF cannot map the new SDFs to another bearer.

A.4.3.2.2 Policy and Charging Enforcement Function (PCEF)

In the 3GPP Access (GTP-based) architecture the PCEF enforce QoS Policies as indicated by the PCRF in accordance to what is stated in clause 6.2.2.1 with the following additions:

– Authorized APN-AMBR enforcement. The PCEF shall enforce the authorized APN-AMBR received via the Gx interface for the total bandwidth usage of non-GBR QCI for the APN.

– Authorized Default EPS Bearer QoS Enforcement. The PCEF receives the authorized QoS for the default bearer over Gx interface. The PCEF enforces it which may lead to the upgrade or downgrade of the default EPS Bearer QoS. The PCEF shall re-evaluate the bearer binding (as defined in clause 6.1.1.4) taking into account the default bearer QoS change and any PCC Rule operation requested by the PCRF.

When the PDN GW is connected via Gn/Gp (and thus handover from UTRAN/GERAN to E‑UTRAN is possible), the PDN-GW shall map QoS parameters of EPS bearers and APN-AMBR (if not received via Gn/Gp) to/from Release 99 and Release 97/Release 98 QoS parameter values of PDP-contexts as specified in Annex E of TS 23.401 [17]. The PDN GW shall mediate Gn/Gp procedures so that PCRF experiences no difference compared to S5/S8 procedures.

Only the GBR per bearer is used for resource reservation (e.g. admission control in the RAN).

The MBR (per PCC rule / per bearer) and the authorized APN-AMBR are used for rate policing.

A.4.3.2.3 Application Function (AF)

The AF instructions to report loss of transmission resources will result in a notification from the PCRF that may include an indication that the transmission resources are lost due to PS to CS handover.

NOTE: The AF action up to notification of termination of transmission resources due to PS to CS handover is application specific. IMS interprets that the PS to CS handover notification as SRVCC.

A.4.3.3 Void

A.4.3.4 IP-CAN bearer and IP-CAN session related policy information

For EPS the IP‑CAN bearer and IP‑CAN session related policy information in table A.4.3.4-1 shall apply in addition to the ones in table 6.4 and table A.4.

A Presence Reporting Area may be defined as a short list of TAs or eNBs and/or ECGI for E-UTRAN, a short list of RAs or SAIs or CGIs for UTRAN, and a short list of RAs or CGIs for GERAN.

Table A.4.3.4-1: PCC related IP-CAN bearer and IP‑CAN session related policy information

Attribute	Description	PCRF permitted to modify the attribute	Scope
Authorized default EPS bearer QoS	Defines the QCI and ARP of the default EPS bearer.	Yes	IP‑CAN session
Subsequent default EPS bearer QoS (NOTE 1)	Defines the QCI and ARP of the default EPS bearer to be applied by the PCEF when the default EPS bearer QoS change time is reached.	No (NOTE 2)	IP‑CAN session
Default EPS Bearer QoS change time (NOTE 1)	Defines the time at which the PCEF shall apply the subsequent default EPS bearer QoS.	No (NOTE 2)	IP‑CAN session
NOTE 1: Both parameters shall be provided together. The PCRF may provide up to four instances of them. NOTE 2: The PCRF may replace all instances of Subsequent default EPS bearer QoS that have been provided previously with a new instruction. There is no operation to modify a previously provided instance of Subsequent default EPS bearer QoS and/or Default EPS Bearer QoS change time.

The purpose of the default EPS bearer related policy information in table A.4.3.4-1 is to provide QCI and ARP that is applicable to the default bearer of an IP‑CAN session. The PCRF may provide the authorized default EPS bearer QoS in every interaction with the PCEF. The PCEF shall apply the authorized default EPS bearer QoS for the IP‑CAN session, including the necessary bearer binding actions.

If dynamic PCC rules are used and the PCEF has indicated that it supports the PCC rule attribute Bind to Default Bearer, the PCRF may provide a subsequent default EPS bearer QoS together with a default EPS bearer QoS change time. When the default EPS bearer QoS change time is reached, the PCEF shall apply the corresponding subsequent default EPS bearer QoS as the new authorized default EPS bearer QoS for the IP-CAN session and perform the necessary bearer binding actions for all of the respective dynamic PCC rules. To keep dynamic PCC rules bound to the default bearer, the PCRF shall include the attribute Bind to Default Bearer in every dynamic PCC rule intended to remain bound to the default bearer.

The PCRF may provide up to four instances of subsequent default EPS bearer QoS.

NOTE 1: In order to reduce the risk for signalling overload, the PCRF can spread the provisioning of subsequent default EPS bearer QoS for many UEs over time.

NOTE 2: The bearer modification is made in the same way as if the PCRF had modified the authorized default EPS bearer QoS at that point in time.

The PCEF shall discard any previously received subsequent default EPS bearer QoS instances on explicit instruction as well as whenever the PCRF provides a new instruction for one or more subsequent changes to the default EPS bearer QoS or any other subsequent parameter.

NOTE 3: In order to provide further subsequent default EPS bearer QoS in a timely fashion the PCRF can use its own clock to issue the desired changes or use the Revalidation time limit parameter (clause 6.4) to trigger a PCEF request for a policy decision.

NOTE 4: For services that depend on specific APN-AMBR and/or QoS for the default EPS bearer (e.g. MPS session) the PCRF is responsible to ensure that no subsequent APN-AMBR or default EPS bearer QoS interfere with the service, e.g. by removing the subsequent APN-AMBR or default EPS bearer QoS before the respective change time is reached.

A.4.3.5 TDF session related policy information

For EPS the TDF session related policy information in table A.4a shall apply in addition to the ones in table 6.4a.

A.4.4 PCC Procedures and Flows

A.4.4.1 Introduction

For the 3GPP Access (GTP-based), an IP‑CAN session is established by the Create Default Bearer message. The IP‑CAN session is terminated when the last EPS bearer of the IP‑CAN session is disconnected.

From the network scenarios listed in clause 7.1, the Case 1 (no Gateway Control Session) applies.

A.4.4.2 IP‑CAN Session Establishment

In the case of IP‑CAN Session Establishment (described in clause 7.2), the PCEF provides to PCRF (in addition to the parameters described in clause 7.2): the User Location Information, Serving Network, Serving-GW address and RAT type.

The PCEF shall also forward the network capability of reporting of changes in CGI/SAI/RAI to the PCRF.

The PCRF includes, in the IP‑CAN Session Establishment Ack, PCC Rules with QCI and ARP matching the Authorized Default EPS Bearer QoS, Authorized APN-AMBR and Authorized Default EPS Bearer QoS. If bearer establishment mode is UE/NW, the PCRF may also include PCC Rules requiring a QCI and ARP different from the Default Bearer QoS and for which NW mode applies.

A.4.4.3 GW (PCEF) initiated IP‑CAN Session termination

The GW (PCEF) initiated IP‑CAN Session termination procedure (described in clause 7.3.2) has no 3GPP specific information.

A.4.4.4 IP‑CAN Session Modification

A.4.4.4.1 IP‑CAN Session Modification; GW (PCEF) initiated

For IP‑CAN session modification (described in clause 7.4.1) the PCEF includes the modification of any of the 3GPP specific information listed in clause A.4.4.2.

If the PS to CS handover indicator is set for an IP-CAN bearer that is deleted, the PCEF reports termination of transmission resources for associated PCC Rules due to PS to CS handover.

The PCRF may provide the following parameters in the Acknowledgement of the IP‑CAN Session Modification to the PDN GW (in addition to the parameters in clause 7.4.1): Authorized APN-AMBR, Authorized Default EPS Bearer QoS.

A.4.4.4.2 IP‑CAN Session Modification; PCRF initiated

The PCRF may provide the following parameters in the Policy and Charging Rule Provision to the PDN GW (in addition to the parameters in clause 7.4.2): Authorized APN-AMBR, Authorized Default EPS Bearer QoS.

Whenever the PCRF modifies the Authorized Default EPS Bearer QoS, the PCRF shall simultaneously modify the QCI and ARP of all PCC Rules that, according to the operator policy, shall have the same QoS as the default bearer.

A modification of the Authorized Default EPS Bearer QoS requires that at least one PCC Rule with a matching QoS can be bound to the default bearer as defined in clause 6.1.1.4.

NOTE: The network configuration can ensure that at least one PCC Rule is bound to the default bearer by applying, either operator policies in the PCRF ensuring that a PCC Rule with matching QoS will be active or in the PCEF ensuring that a predefined PCC Rule not known to the PCRF is bound to the default bearer.