4.1 IP-CAN Session Establishment

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

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This subclause is applicable if a new IP-CAN Session is being established.

Figure 4.1.1: IP-CAN Session Establishment

1. The BBERF may initiate a Gateway Control Session Establishment procedure as defined in subclause 4.4.1 (applicable for cases 2a during initial attach and 2b, as defined in subclause 4.0), if appropriate. In this step, the PCRF determines whether the cases 2a or 2b applies, as defined in subclause 4.0.

2. The PCEF receives an Establish IP-CAN Session Request. The form of the Establish IP-CAN Session Request depends upon the type of the IP-CAN.

3. For the non-roaming case, and for the case when the UE is roaming in a Home Routed scenario, the PCEF informs the H-PCRF of the IP-CAN Session establishment. The PCEF starts a new Gx session by sending a CCR to the H-PCRF using the CC-Request-Type AVP set to the value INITIAL_REQUEST. The PCEF provides UE identity information, PDN identifier, the UE Ipv4 address and/or UE Ipv6 prefix and, if available, the PDN connection identifier, IP-CAN type, RAT type and/or the default charging method and additional charging parameters as defined in subclause 4.5.1 of 3GPP TS 29.212 [9] and may send charging characteristics if available. The PCEF provides, when available, the Default-EPS-Bearer-QoS and the APN-AMBR to the PCRF. The PCEF may provide the applicable TDF routing information in TDF-Information AVP. If the UE has declared support for the extended TFT filter format and the PCEF does not prevent the use thereof, the PCE F shall indicate that the support for extended TFT filters is available in the IP-CAN session. For types of IP-CAN, where the H-PCRF can be in control of IP-CAN Bearers, e.g. GPRS, the PCEF also provides a new bearer identifier and information about the requested bearer, such as QoS. If applicable for the IP-CAN type, it will also provide information to indicate whether NW-initiated bearer control procedures are supported, if available. The PCRF links the Gx session for the new IP-CAN session with the corresponding Gateway Control Session as defined in subclause 4.0. The PCRF maintains aligned set of PCC and QoS rules in the PCEF and BBERF(s) as applicable for the case. For case 2a and if IP flow mobility is supported, the PCEF provides, when available, the IP flow mobility routing rules. For case 1 and if NBIFOM is supported, the PCEF provides, when available, the NBIFOM support and NBIFOM mode information. If available, the PCEF provides a timestamp corresponding to the time at which the request was initiated by the originating node, and additionally the PCEF can include the maximum wait time as defined in subclause 4.5.1 of 3GPP TS 29.212 [9].

For the case when the UE is roaming in a Visited Access scenario, steps 3a~3c are executed instead of step 3.

3a. The PCEF informs the V-PCRF of the establishment of the IP-CAN session. The PCEF starts a new Gx session by sending a CCR to the V-PCRF with the CC-Request-Type AVP set to the value INITIAL_REQUEST. The parameters for CCR as listed in step 3 are applicable here.

3b. The V-PCRF determines that the request is for a roaming user and concludes the IP-CAN session uses visited access. V-PCRF stores the received information.

3c. If there is not an already established S9 session for this roaming user, the V-PCRF sends a CCR to the H-PCRF with the CC-Request-Type AVP set to the value INITIAL_REQUEST. The V-PCRF includes the Subsession-Enforcement-Info AVP within the CCR with a new S9 subsession identifier assigned by the V-PCRF to this IP-CAN session within the Subsession-Id AVP, and the Subsession-Operation AVP set to the value ESTABLISHMENT.

If there is an already established S9 session for this roaming user, the V-PCRF sends a CCR to the H-PCRF with the CC-Request-Type AVP set to the value UPDATE_REQUEST. The V-PCRF includes the Subsession-Enforcement-Info AVP within the CCR with a new S9 subsession identifier assigned by the V-PCRF to this IP-CAN session within the Subsession-Id AVP, and the Subsession-Operation AVP set to the value ESTABLISHMENT.

4. The H-PCRF stores the information received in the CCR. For cases 2a and 2b, the H-PCRF links the Gx session with the Gateway Control Session(s).

NOTE 1: In the case 2a, when an additional PDN connection is established, the Gx session is linked with the already established Gateway Control Session.

5. If the H-PCRF requires subscription-related information and does not have it, the H-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), QoS information, PCC Rules information and may include MPS EPS Priority, MPS Priority Level and IMS Signalling Priority for establishing a PS session with priority.

NOTE 2: 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. If the PCRF determines that the policy decision depends on the status of the policy counters available at the OCS and no Sy session yet has been established for this subscriber, the PCRF sends an Initial Spending Limit Report Request as defined in subclause 4.7.1. If the Sy sesson is already established for this subscriber, the PCRF may send, if required, an Intermediate Spending Limit Report Request as defined in subclause 4.7.2.

8. The H-PCRF selects or generates PCC Rule(s) to be installed. The H- PCRF may also make a policy decision by deriving an authorized QoS and by deciding whether service flows described in the PCC Rules are to be enabled or disabled. If MPS EPS Priority, MPS Priority Level, and IMS Signalling Priority are present for the user, the PCRF takes the information into account. If NBIFOM is supported, the PCRF determines whether the NBIFOM applies to the IP-CAN session and selects the NBIFOM mode.

9. The H-PCRF stores the selected PCC Rules. The H-PCRF selects the Bearer Control Mode that will apply during the IP-CAN session if applicable for the particular IP-CAN. If the H-PCRF controls the binding of IP-CAN Bearers, the H-PCRF stores information about the IP-CAN Bearer to which the PCC Rules have been assigned. If the BBERF/PCEF controls the binding of IP-CAN bearers, the H-PCRF may derive the QoS information per QCI applicable to that IP-CAN session for non-GBR bearers.

10. When user profile configuration indicates that Application Detection and Control function is enabled, the H-PCRF makes the policy decision for the application detection and control. For the non-roaming case, or for the case when the UE is roaming in a Home Routed scenario, the H-PCRF selects the applicable PCC Rules to be provided for application detection and control for the PCEF supporting ADC feature, or the applicable ADC rules for the solicited application reporting with a TDF. For the case when the UE is roaming in a Visited Access scenario, the H-PCRF selects the applicable PCC Rules to be provided for application detection and control. For solicited application reporting with a TDF, the H-PCRF finds the TDF by using the TDF-Information AVP received from the PCEF in step 3, or, if not received, using a pre-configured TDF address.

11. Only applicable for non-roaming case, and for the case when the UE is roaming in a home routed case, In case of solicited application reporting with a TDF, the PCRF initiates a TDF Session Establishment procedure, according to subclause 4.6.1, with the selected TDF.

12. If traffic steering control over St applies andthe H-PCRF determines that traffic steering control information is needed for the IP-CAN session, the PCRF initiates an St session establishment procedure according to subclause 4.9.1 with the TSSF. The TSSF identifier is pre-configured on the PCRF per e.g. PCEF.

13. For the non-roaming case, and for the case when the UE is roaming in a Home Routed scenario, the H-PCRF provisions the PCC Rules to the PCEF using CCA. The H-PCRF also provides the selected Bearer Control Mode if applicable for the particular IP-CAN and if available, the QoS information per QCI. If the PCEF has indicated that the support for extended TFT filters is available in the IP-CAN session, then the PCRF may, by indicating the PCRF support for extended TFT filters, enable the use of the extended TFT filter format in the IP-CAN session. The PCRF may also provide event triggers listing events for which the PCRF desires PCC Rule Requests. Furthermore, the PCRF may provide authorized QoS including the APN-AMBR and the Default-EPS-Bearer-QoS, User Location Information, user CSG information (if received from the BBERF) and Presence Reporting Area Information. If usage monitoring is enabled, the H-PCRF may provide the applicable thresholds for usage monitoring control at PCEF within the Usage-Monitoring-Information AVP. If NBIFOM is supported, the H-PCRF provides the decision on whether the NBIFOM is supported and the selected NBIFOM mode if applicable.

For types of IP-CAN, where the PCRF controls IP-CAN Bearers, e.g. GPRS, the PCRF indicates the IP-CAN Bearer where the PCC Rules are to be installed and that the authorized QoS refers to. Otherwise, the PCRF operates without any further reference to any specific bearer.

If the PCEF supports Application Detection and Control feature, the PCRF provisions the applicable PCC Rules to the PCEF for the corresponding IP-CAN session.

If online charging is applicable then the PCEF requests credit information from the OCS over the Gy interface. If the PCEF receives credit re-authorisation triggers from the OCS then, for case 2b, it requests the PCRF via a CCR message to provision the triggers at the BBERF. The triggers to be provisioned are specified in the Event-Report-Indication AVP in the CCR message.

For the case when the UE is roaming in a Visited Access scenario, steps 13a -13g are executed.

13a. The PCC Rules, if they were selected in step 9, are provisioned by the H-PCRF to the V-PCRF by using a CCA. The H-PCRF includes PCC Rules in the Subsession-Decision-Info AVP of the CCA, along with the S9 subsession identifier as received in step 3c within the Subsession-Id AVP. Other parameters listed in step 9 are also applicable here.

13b. The V-PCRF enforces visited operator policies regarding QoS authorization requested by the H-PCRF as indicated by the roaming agreements.

13c. In case of TDF, if Application Detection and Control function is enabled for the IP-CAN session, the V-PCRF extracts ADC rules from the received PCC rules from the H-PCRF and stores the ADC rules.

13d. The V-PCRF informs the H-PCRF when a request has been denied and may provide the acceptable QoS Information for the service.

13e. The H-PCRF acknowledges the CCR and may additionally include new or modified PCC rules to the V-PCRF. When user profile configuration indicates that Application Detection and Control function is enabled, some of those PCC Rules may be dedicated for application detection and control.

13f. In case of solicited application reporting with a TDF, the V-PCRF initiates a TDF Session Establishment procedure, according to subclause 4.6.1, with the selected TDF and provides ADC Rules extracted from the corresponding PCC Rules.

13g. The V-PCRF provisions PCC rules received from the H-PCRF to the PCEF by using CCA. The parameters listed in step 11a are applicable here, User Location Information and user CSG information (if received from the BBERF).

NOTE 3: From this point and onward, the PCRF is responsible for keeping the active PCC, ADC and QoS rules aligned.

14. If case 2a or 2b applies, the PCRF aligns the set of QoS rules at the BBERF with the set of active rules at the PCEF.

15. The PCEF installs the received PCC Rules. The PCEF also enforces the authorized QoS and enables or disables service flows according to the flow status of the corresponding PCC Rules. If QoS information is received per QCI, PCEF sets the upper limit accordingly for the MBR that the PCEF assigns to the non-GBR bearer(s) for that QCI. In case of PCEF supporting Application Detection and Control feature, the PCEF enforces the application detection and control.

16. The PCEF sends a response to the Establish IP-CAN Session Request.
For GPRS, the GGSN accepts the PDP Context Request based on the results of the authorisation policy decision enforcement. 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.

NOTE 4: The PCRF can reject the IP-CAN session establishment, e.g. the PCRF cannot obtain the subscription-related information from the SPR and the PCRF cannot make the PCC rule decisions, as described in 3GPP TS 29.212 [9].

PCEF can also enforce active preconfigured PCC rules which are not know to the PCRF.

The PCEF can also reject the IP-CAN session establishment, e.g. there is no active PCC rule for the IP-CAN session as specified in 3GPP TS 23.203 [2].