Section: .1 PDN GW initiated bearer modification with bearer QoS update
Content: The PDN GW initiated bearer modification procedure (including EPS Bearer QoS update) for a GTP based S5/S8 is depicted in figure 5.4.2.1-1. This procedure is used in cases when one or several of the EPS Bearer QoS parameters QCI, GBR, MBR or ARP are modified (including the QCI or the ARP of the default EPS bearer e.g. due to the HSS Initiated Subscribed QoS Modification procedure, as described in clause 5.4.2.2) or to modify the APN-AMBR. Modification from a QCI of resource type non-GBR to a QCI of resource type GBR and vice versa is not supported by this procedure. NOTE 1: The QCI of an existing dedicated bearer should only be modified if no additional bearer can be established with the desired QCI. Figure 5.4.2.1-1: Bearer Modification Procedure with Bearer QoS Update NOTE 2: Steps 3-10 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For a PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [2]. Steps 1, 2, 11 and 12 concern GTP based S5/S8. 1. If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN GW. This corresponds to the initial steps of the PCRF-Initiated IP-CAN Session Modification procedure or to the PCRF response in the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6], up to the point that the PDN GW requests IP-CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy. 2. The PDN GW uses this QoS policy to determine that the authorized QoS of a service data flow has changed or that a service data flow shall be aggregated to or removed from an active bearer. The PDN GW generates the TFT and updates the EPS Bearer QoS to match the traffic flow aggregate. The PDN GW then sends the Update Bearer Request (PTI, EPS Bearer Identity, EPS Bearer QoS, APN-AMBR, TFT, Maximum Packet Loss Rate (UL, DL)) message to the Serving GW. The Procedure Transaction Id (PTI) parameter is used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. For APN-AMBR, the EPS bearer identity must refer to a non-GBR bearer. For a QCI=1 bearer, the Maximum Packet Loss Rate (UL, DL) may be provided by the PDN GW as described in TS 23.203[ Policy and charging control architecture ]  [6]. 3. The Serving GW sends the Update Bearer Request (PTI, EPS Bearer Identity, EPS Bearer QoS, TFT, APN-AMBR, Maximum Packet Loss Rate (UL, DL)) message to the MME. If the UE is in ECM-IDLE state the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4-7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. If only the QoS parameter ARP is modified and if the UE is in ECM IDLE state the MME shall skip the Network Triggered Service Request. In that case the following steps 4-9 are also skipped and the MME sends an Update Bearer Response to the Serving GW. If extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3), and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends an Update Bearer Response with a rejection cause indicating that the UE is temporarily not reachable due to power saving and, if a Delay Tolerant Connection indication was set for the PDN connection, the MME sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving GW to the PDN GW. In this case, the steps 4-11 are skipped. NOTE 3: If ISR is activated and the Serving GW does not have a downlink S1-U and the SGSN has notified the Serving GW that the UE has moved to PMM-IDLE or STANDBY state, the Serving GW sends Downlink Data Notification to trigger MME and SGSN to page the UE (as specified in clause 5.3.4.3) before sending the Update Bearer Request message. 4. The MME builds a Session Management Request including the PTI, EPS Bearer QoS parameters (excluding ARP), TFT, APN-AMBR, EPS Bearer Identity and a WLAN offloadability indication. If the UE has UTRAN or GERAN capabilities and the network supports mobility to UTRAN or GERAN, the MME uses the EPS Bearer QoS parameters to derive the corresponding PDP context parameters QoS Negotiated (R99 QoS profile), Radio Priority and Packet Flow Id and includes them in the Session Management Request. If the UE indicated in the UE Network Capability it does not support BSS packet flow procedures, then the MME shall not include the Packet Flow Id. If the APN-AMBR has changed the MME may update the UE-AMBR if appropriate. The MME then sends the Bearer Modify Request (EPS Bearer Identity, EPS Bearer QoS, Session Management Request, UE-AMBR, Maximum Packet Loss Rate (UL, DL)) message to the eNodeB. The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23. 5. The eNodeB maps the modified EPS Bearer QoS to the Radio Bearer QoS. It then signals a RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE. The UE shall store the QoS Negotiated, Radio Priority, Packet Flow Id, which it received in the Session Management Request, for use when accessing via GERAN or UTRAN. If the APN-AMBR has changed, the UE stores the modified APN-AMBR value and sets the MBR parameter of the corresponding non-GBR PDP contexts (of this PDN connection) to the new value. The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE may provide EPS Bearer QoS parameters to the application handling the traffic flow(s). The application usage of the EPS Bearer QoS is implementation dependent. The UE shall not reject the Radio Bearer Modify Request on the basis of the EPS Bearer QoS parameters contained in the Session Management Request. The UE shall set its TIN to "GUTI" if the modified EPS bearer was established before ISR activation. NOTE 4: The details of the Radio Bearer QoS are specified in TS 36.300[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [5]. 6. The UE acknowledges the radio bearer modification to the eNodeB with a RRC Connection Reconfiguration Complete message. 7. The eNodeB acknowledges the bearer modification to the MME with a Bearer Modify Response (EPS Bearer Identity, PSCell ID) message. With this message, the eNodeB indicates whether the requested EPS Bearer QoS could be allocated or not. The MME shall be prepared to receive this message either before or after the Session Management Response message (sent in step 9). The PSCell ID is included if Dual Connectivity is active for the UE in the RAN. 8. The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB. 9. The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME. 10. Upon reception of the Bearer Modify Response message in step 7 and the Session Management Response message in step 9, the MME acknowledges the bearer modification to the Serving GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI), PSCell ID) message. 11. The Serving GW acknowledges the bearer modification to the PDN GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message. 12. If the Bearer modification procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not by sending a Provision Ack message allowing the completion of the PCRF-Initiated IP-CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6], after the completion of IP-CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. If the Bearer modification is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message. NOTE 5: The exact signalling of step 1 and 12 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the bearer activation procedure are to be specified in TS 23.203[ Policy and charging control architecture ]  [6]. Steps 1 and 12 are included here only for completeness.