The Gx reference point enables the signalling of PCC rules, which govern the PCC behaviour and it supports the following GPRS-specific functions:

• Indication of PDP context activation, modification and deactivation.

A container may be closed and a new container opened by the triggering of event triggers.

For GPRS the PCEF shall initiate one credit management session for each PDP context. For GPRS the credit re-authorisation triggers in Table A.1-1 shall apply in addition to the ones in Table 6.1. They are applicable both in case of PCEF and in case of TDF.

If the Location change trigger for CGI / SAI or RAI is armed, the GGSN should request the SGSN to report any changes in location to the level indicated by the trigger according to the procedures described in TS 23.060. If credit re-authorization triggers and event triggers require different levels of reporting of location change for different PDP contexts for a single IP-CAN session, the SGSN reports location changes to the highest level of detail required. However, the GGSN should not trigger a credit re-authorization if the report received is more detailed than requested by the OCS. If the User CSG Information change in CSG cell trigger is armed, the GGSN should request the SGSN 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 GGSN should request the SGSN 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 GGSN should request the SGSN 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 SGSN should be changed to the highest level of detail required. Change of UE presence in Presence Reporting Area is not applicable for GPRS IP-CAN.

For GPRS the event triggers in Table A.2 shall apply in addition to the ones in Table 6.2 at the PCEF upon the request of the PCRF.

If the Location change trigger is armed, the GGSN should request the SGSN to report any changes in location to the level indicated by the trigger according to the procedures described in TS 23.060. If credit-authorization triggers and event triggers require different levels of reporting of location change for different PDP contexts for a single UE, the SGSN reports location changes to the highest level of detail required. However, the GGSN should not trigger a request for PCC rules if the report received is more detailed than requested by the PCRF. For GPRS, the traffic mapping information is represented by the TFT information. For GPRS, the loss/recovery of transmission resources is indicated by a PDP context modification changing the 'Maximum bitrate' UMTS QoS parameter to/from 0 kbit/s (as described in the PDP context preservation procedure in TS 23.060). The User Location Report in the Access Network Information Reporting contains the CGI/SAI and when the PDP context 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 GGSN should request the SGSN 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 GGSN should request the SGSN 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 GGSN should request the SGSN 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 SGSN should be changed to the highest level of detail required. Change of UE presence in Presence Reporting Area is not applicable for GPRS IP-CAN.

For GPRS the AF instruction to report changes of the IP-CAN bearer level information Type of IP-CAN shall also result in a reporting of RAT type changes, even if the IP-CAN type is unchanged.

For GPRS the AF instruction to report changes of the IP-CAN bearer level information Type of IP-CAN will also result in a reporting of RAT type changes, even if the IP-CAN type is unchanged. 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.

Void.

The PCRF associates, at activation, a PCC rule with a PDP context at the PCEF.

The UE initiated IP-CAN Session termination procedure (described in clause 7.3.1) is triggered at the GGSN by receiving a Delete PDP Context request message if this is the deletion of the last PDP Context for the IP Address or the Teardown Indicator in the Delete PDP Context Request indicates that all PDP contexts that share the same IP address should be deactivated. All PDP Contexts in the IP-CAN Session are deleted in the GGSN. The IP Address of the UE is released. The Delete PDP Context Response message, indicating that the PDP context(s) is deleted, is sent to the SGSN.

The GW initiated IP-CAN Session termination procedure (described in clause 7.3.2) is triggered if the GGSN detects that the IP-CAN Session shall be terminated. The Delete PDP Context request message is sent by the GGSN to the SGSN. This may be the deletion of the last PDP Context for the IP Address. If not, the GGSN shall set the Teardown Indicator in the Delete PDP Context Request message to indicate that all PDP contexts that share that same IP address shall also be deactivated. All PDP Contexts in the IP-CAN Session are deleted. The IP Address of the UE is released. The Delete PDP Context Response, indicating that the PDP context(s) is deleted, is received from the SGSN.

The GW (PCEF) initiated IP-CAN Session modification procedure (described in clause 7.4.1) is triggered at the GGSN by receiving one of the following messages:

• Create PDP Context Request message;
• Update PDP Context Request message;
• Delete PDP Context Request message;
• a Change Notification message (indicating the new CGI, SAI or RAI) - see TS 23.060.

In case of a Create PDP Context Request message, the modification of the IP-CAN Session is the addition of a new PDP Context to the IP-CAN Session. The new PDP Context is added with specific QoS requirements and traffic mapping information (TFT). A Create PDP Context Response message, indicating that a new PDP context is created, is sent to the SGSN. The response may include any changes in QoS according to bearer binding and policy enforcement. In case of an Update PDP Context Request, a PDP Context in the IP-CAN Session is modified. The modification may include modifying the QoS and/or the traffic mapping information. The Update PDP Context Response message, indicating that a PDP context is modified, is sent to the SGSN. The response may include any changes in QoS according to bearer binding and policy enforcement. In case of a Delete PDP Context Request message, a PDP Context in the IP-CAN Session is deleted. The Delete PDP Context Response message, indicating that a PDP context is deleted, is sent to the SGSN. .If the PS to CS handover indicator is set in a Delete PDP context request message , the PCEF reports termination of transmission resources for associated PCC Rules due to PS to CS handover. A Change Notification message indicating a change in CGI / SAI or RAI information is received when there are only changes regarding the current location of the UE. A change in CGI / SAI or RAI may also be notified within other session management messages. The PCRF may provide the Authorized APN-AMBR in the Acknowledgement of the IP-CAN Session Modification to the GW (in addition to the parameters in clause 7.4.1). Based on operator policy the PCRF may re-authorize MBR/APN-AMBR.

The PCRF initiated IP-CAN Session modification procedure (described in clause 7.4.2) may result in a GGSN initiated PDP Context Modification or Deactivation or a Network Requested secondary PDP Context Activation. If a PDP Context in the IP-CAN Session needs to be modified, the GGSN sends an Update PDP Context Request message. The modification may include modifying the QoS negotiated, negotiated Evolved ARP or the required CGI/SAI/RAI change reporting. The Update PDP Context Response message, indicating that a PDP context is modified, will be received from the SGSN. If a PDP Context in the IP-CAN Session needs to be deleted, the GGSN sends a Delete PDP Context Request message. The Delete PDP Context Response message will be received from the SGSN. If the PCEF bearer binding yields that a new PDP context is required, the PCEF shall initiate the Network Requested secondary PDP Context Activation procedure. The PCRF may provide the Authorized APN-AMBR in the Policy and Charging Rule Provision to the GW (in addition to the parameters in clause 7.4.2).