D.3 PCC Procedures

29.2133GPPPolicy and charging control signalling flows and Quality of Service (QoS) parameter mappingRelease 17TS

D.3.1 IP-CAN Session Modification

D.3.1.1 Network-initiated IP-CAN Session Modification

Network-initiated IP-CAN session modification is executed according to clause 4.3.1.1 with the following differences:

– The timer in step 4 will also be activated waiting for one of the following cases:

– If the authorized QoS for an IP-CAN bearer is changed or

– If one or more Flow Descriptions need to be added, deactivated or removed in any of the PCC rules bound to an IP-CAN bearer

– If the timer in step 4 expires and the PCRF still requires additional filter information coming from the UE in order to decide on bearer binding for new PCC rules to be installed, all subsequent steps in figure 4.3.1.1.1 shall not be executed, and further reactions of the PCRF are left unspecified. As a possible option, the PCRF could abort the AF session.

– When the PCRF performs the bearer binding, once the PCC rules are selected, the PCRF identifies the IP-CAN bearer for each of the PCC rules and the authorized QoS. The PCRF may provision PCC Rules and authorized QoS for several IP-CAN Bearers within the same RAR command.

– For step 9, IP-CAN session signalling, the subsequent steps are executed separately for each IP-CAN bearer under the following conditions:

– if all PCC rules bound to a PDP context have been removed or deactivated (PDP Context deactivation is applicable)

– if one or more PDP contexts have to be modified

– if in UE/NW Bearer Control Mode, the GGSN needs to establish a new PDP context(PDP Context establishment is applicable) if the bearer binding is located at the PCEF.

The GGSN initiates the procedure to Create/Update or Terminate PDP Context Request message to the SGSN. If in the case of updating the PDP Context the authorized QoS for the bearer has changed, the GGSN will modify the UMTS QoS parameters accordingly.

When the procedure in step 9 is completed and requires notifications from the GW, for an IP-CAN Bearer termination in UE-Only Bearer Control Mode, the GGSN sends a Diameter CCR with the Bearer-Identifier and Bearer-Operation AVPs to indicate “Termination”.

D.3.1.2 PCEF-initiated IP-CAN Session Modification

PCEF-initiated IP-CAN Session Modification procedure shall take place according to clauses 4.3.2.1 and 4.3.2.2 except for those procedures initiated by the UE, as described in the clauses below.

D.3.1.2.1 UE-initiated IP-CAN Bearer Establishment or IP-CAN Bearer Modification

This clause is applicable for the establishment of a new IP-CAN Bearer (other than the one which created the IP-CAN session) and for the modification of an already established IP-CAN Bearer. The signalling flows for these cases are as per Figure 4.3.1.2.1.

A bearer-event-initiated Request of PCC Rules occurs when a new bearer is established or when an existing bearer is modified. For GPRS, these are PDP Context Modification(s) or secondary PDP context Activation(s). An IP-CAN Session modification triggers a PCC Rule request only if the PCRF has previously requested a PCC Rule request for the given modification event.

Figure D.3.1.2.1: UE-initiated IP-CAN Bearer Establishment and Modification.

1. The GW receives IP-CAN Bearer signalling that is a trigger for a PCC Rule request. For GPRS, the GGSN receives a secondary Establish PDP Context Request or an Update PDP Context Request.

2. The GW informs the PCRF of the modification of the IP-CAN Session due to the IP-CAN Bearer signalling in step 1, using a Diameter CCR with the CC-Request-Type AVP set to the value UPDATE_REQUEST. The GW reuses the existing Gx DCC session corresponding to the IP-CAN Session.

If the IP-CAN Bearer signalling in step 1 established a new IP-CAN Bearer, the GW assigns a new bearer identifier to this IP-CAN Bearer. The GW provides information about the new or modified bearer, e.g. requested QoS and TFT filters. If the event that caused the bearer modification applies uniquely to that bearer and PCRF performs the bearer binding, then, the bearer identifier should be provided within the CCR. If no bearer identifier is provided, the event trigger will apply to the IP-CAN session.

3. The PCRF stores the received information in the Diameter CCR.

4. The PCRF binds the IP-CAN Session to existing of AF session(s) using the information received from the GW and the Service Information included in the stored PCC rules, which was previously received from the AF(s) , as depicted in figure 4.3.1.1.1.
The PCRF also binds the IP-CAN Bearers within the IP-CAN Session to all matching IP flow(s) of existing AF session(s) using the bearer information received from the GW and the Service Information received from the AF(s). If IP flow(s), which have previously been bound to other bearers, have been bound to the modified bearer, PCC Rules in other bearer(s) may need to be removed. For GPRS, an IP flow may need to be removed if a matching higher priority TFT filter in the newly established PDP context takes precedence over a matching lower priority TFT filter in another PDP context. Furthermore, if IP Flow(s), which have previously been bound to the modified bearer are be bound to other bearer(s), PCC Rules may need to be installed in other bearers. For GPRS, an IP flow may be bound to another PDP context if it was previously bound to the modified PDP context due to a removed higher priority TFT filter, and a lower priority TFT filter in the other PDP context matches the IP flow.

5. If the PCRF requires subscription-related information and does not have it, the PCRF sends a request to the SPR in order to receive the information.

6. The SPR replies with the subscription related information containing the information about the allowed service(s) and PCC Rules information.

NOTE: For steps 5 and 6: The details associated with the Sp reference point are not specified in this Release. The SPR’s relation to existing subscriber databases is not specified in this Release.

7. For IP CAN session modification, if the AF requested a notification of the corresponding event at the initial authorisation of the AF session, the PCRF shall sent a Diameter RAR with the Specific-Action AVP set to indicate the trigger event that caused the request.

8. If step 7 happens, the AF replies with a Diameter RAA and may provide updated service information within.

9. The PCRF selects the new PCC Rule(s) to be installed. The PCRF can also identify existing PCC Rules that need to be modified or removed. The PCC Rules may relate to any of the matching AF sessions identified in step 4 or may exist in the PCRF without matching to any AF session. The PCRF may also make a policy decision by defining an authorized QoS and by deciding whether service flows described in the PCC Rules are to be enabled or disabled.
For types of IP-CAN, where the PCRF controls IP-CAN Bearers, e.g. GPRS, the PCC Rules may affect the IP-CAN Bearer identified in the CCR of step 2 or any other IP-CAN Bearer identified in step 4.

10. The PCRF stores the modified PCC Rules.

11. The PCC Rules are provisioned by the PCRF to the GW using Diameter CCA. The PCRF may also provide authorized QoS. The PCRF identifies the affected IP-CAN Bearer for each of the PCC Rules and the authorized QoS. The PCRF may provision PCC Rules and authorized QoS for several IP-CAN Bearers within the same CCA.

12. The GW installs the received PCC Rules. The GW also enforces the authorized QoS and enables or disables service flow according to the flow status of the corresponding PCC Rules.

13. The GW sends a response to the IP-CAN Bearer signalling in step 1.
For GPRS, the GGSN accepts the secondary Establish PDP Context Request or the Update PDP Context Request based on the results of the authorisation policy decision enforcement and sends an Establish PDP Context Response or Update PDP Context Response. If the requested QoS parameters do not correspond to the authorized QoS, the GGSN adjusts (downgrades/upgrades) the requested UMTS QoS parameters to the authorized values.

The PCRF may have decided in step 4 to modify PCC Rules and/or authorized QoS of other IP CAN bearers than the IP-CAN Bearer identified in the CCR of step 2. For each such other IP-CAN Bearer identified in step 4, the GGSN executes the following steps.

14. The PCRF may start a timer to wait for PDP context modification requests from the UE.

15. The PCRF interacts with the GW according to figure 4.3.1.1.1.

D.3.1.2.2 UE-initiated IP-CAN Bearer Termination

This clause is applicable if an IP-CAN Bearer is being released while other IP-CAN Bearers and thus the IP-CAN Session are not released.

For the termination of IP-CAN Bearers, three cases are covered:

– Bearer release that does not cause service data flow(s) within an AF session to be disabled;

– Bearer release that causes at least one but not all the service data flow(s) within an AF session to be disabled; and

– Bearer release that causes all the service data flows within an AF session to be disabled.

A Bearer release may not cause a service data flow within this bearer to be disabled if the IP flow can be bound to another bearer. For GPRS, an IP flow can be bound to another PDP context if a lower precedence TFT filter matching the IP flow is installed at the other PDP context.

Figure D.3.1.2.2: UE-Initiated IP-CAN Bearer Termination

1. The GW receives a Remove IP-CAN Bearer Request that request the deactivation of an IP-CAN Bearer while other IP-CAN Bearers and thus the IP-CAN Session are not released. The form of the Remove IP-CAN Bearer Request depends upon the type of the IP-CAN. For GPRS, the GGSN receives a Delete PDP Context Request.

2. The GW sends a Diameter CCR message with the CC-Request-Type AVP set to the value UPDATE_REQUEST to the PCRF, indicating the IP-CAN Bearer termination.

3. The PCRF identifies the IP flows bound to the removed bearer and updates the stored bearer information. The PCRF re-evaluates the binding of IP flows, as IP flows may now be bound to other bearers. For GPRS, an IP flow may be bound to another PDP Context if it was previously bound to the removed PDP context due to a higher priority TFT filter, and a lower priority TFT filter in another PDP context matches the IP flow.

The following steps 4 and 5 are performed for each of the other bearers identified in step 3:

4. The PCRF selects the PCC Rule(s) to be installed or modified for the affected bearer. The PCRF may also update the policy decision for this bearer.

5. The PCRF stores the updated PCC Rules for the affected bearer.

6. The PCRF acknowledges the bearer termination by sending a Diameter CCA message.
The PCRF provides PCC Rules and possibly updated authorized QoS for each of the other bearers identified in step 3. The PCRF identifies the affected IP-CAN Bearer for each of the PCC Rules and the authorized QoS.

7. The GW removes those PCC Rules, which have not been moved to other IP CAN bearers by the CCA message and are installed in the IP-CAN bearer, for which a termination has been requested in step 1.

8. The GW sends a Remove IP-CAN Bearer Response. For GPRS, the GGSN sends the Delete PDP Context Response message.

9. It the PCRF has provided PCC Rules and possibly updated authorized QoS for other bearers in step 6, the GW installs or modifies the identified PCC Rules. The GW also enforces the authorized QoS and enables or disables service flow according to the flow status of the corresponding PCC Rules.

The following steps 10 to 13 or 10a to 13a apply for the case where at least one IP Flow within an AF session is being disabled, i.e. if the IP Flow is not bound to any other bearer that is still established. The steps shall be performed separately for each ongoing AF session that is affected by the bearer release as explained below.

If all IP flow(s) within the AF session are disabled by the bearer release:

10. The PCRF indicates the session abort to the AF by sending a Diameter ASR message to the AF.

11. The AF responds by sending a Diameter ASA message to the PCRF.

12. The AF sends a Diameter STR message to the PCRF to indicate that the session has been terminated.

13. The PCRF responds by sending a Diameter STA message to the AF.

If at least one but not all of the IP flow(s) within the AF session are disabled by the bearer release, and the AF has requested notification of bearer removal:

10a. The PCRF indicates the release of the bearer by sending a Diameter RAR to the AF.

11a. The AF responds by sending a Diameter RAA to the PCRF.

12a. The AF may send an AAR to the PCRF to update the session information.

13a. If step 12a occurs, the PCRF responds by sending a AAA to the AF.

Annex E (normative):
Fixed Broadband Access Interworking with EPC