Section: 5.4.5 UE requested bearer resource modification
Content: The UE requested bearer resource modification procedure for an E-UTRAN is depicted in figure 5.4.5-1. The procedure allows the UE to request for a modification of bearer resources (e.g. allocation or release of resources) for one traffic flow aggregate with a specific QoS demand. Alternatively, the procedure allows the UE to request for the modification of the packet filters used for an active traffic flow aggregate, without changing QoS. If accepted by the network, the request invokes either the Dedicated Bearer Activation Procedure, the Bearer Modification Procedure or a dedicated bearer is deactivated using the PDN GW Initiated Bearer Deactivation Procedure. The procedure is used by the UE when the UE already has a PDN connection with the PDN GW. A UE can send a subsequent Request Bearer Resource Modification Message before the previous procedure is completed. The UE requested bearer resource modification procedure is used to indicate the change of 3GPP PS Data Off UE Status to the PDN GW via the PCO, only if the UE has been previously informed that the PDN GW supports the 3GPP PS Data Off feature. When a UE supports only Control Plane CIoT EPS Optimisation as defined in clause 5.3.4B the UE need not support the UE requested bearer resource modification procedure in order to modify the traffic flow aggregate, as the UE does not support any DRBs. The UE may need to support UE requested bearer resource modification procedure for other purposes, e.g. header compression negotiation, see TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [46]. The UE supporting 15 EPS bearers as defined in clause 4.12 shall not initiate a UE requested bearer resource modification procedure that would trigger the establishment of a new EPS bearer, if it has already 8 EPS bearers established and the UE has not received an Indication for support of 15 EPS bearers per UE or has received cause #65 "maximum number of EPS bearers reached". In this procedure the UE signals a Traffic Aggregate Description (TAD) which is a partial TFT, together with a Procedure Transaction Identifier (PTI), and an EPS Bearer Identity (when the TAD operation is modify, delete or add to an existing packet filter). When the TAD operation is modify or delete, the packet filter identifiers of the TAD are the same as the TFT packet filter identifiers of the referenced EPS Bearer (as the concatenation of the TFT packet filter identifier and the EPS Bearer identifier represents a unique packet filter identifier within the PDN connection), for which resources are being modified. The TAD is released by the UE after it has received a TFT related to the current PTI from the network. Figure 5.4.5-1: UE requested bearer resource modification NOTE 1: Steps 1, 2, and 5 are common for architecture variants with GTP-based S5/S8 and PMIP-based S5/S8. The procedure steps marked (A) differ in the case that PMIP-based S5/S8 is employed and is defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [2]. If the bearer resource modification procedure is initiated for re-negotiation of header compression configuration for Control Plane CIoT EPS Optimisation, the MME shall not send Bearer Resource Command message to the Serving GW. In this case, the Bearer Modification Procedures (according to clause 5.4.3) is invoked and only the steps from 4 to 7 are performed. 1. The UE sends a Request Bearer Resource Modification (LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the MME. If the UE was in ECM-IDLE mode, this NAS message is preceded by the Service Request procedure. The TAD indicates one requested operation (add, modify, or delete packet filters). If traffic flows are added, the TAD includes the packet filter(s) (consisting of the packet filter information including packet filter precedence, but without a packet filter identifier) to be added. The UE also sends the QCI requested and GBR, if applicable, for the added traffic flows. If the UE wants to link the new packet filter(s) to an existing packet filter to enable the usage of existing bearer resources for the new packet filter(s), the UE shall provide an existing packet filter identifier together with the new packet filter(s). If the new packet filter(s) are not linked to an existing packet filter the UE shall provide at least one UL packet filter in the TAD. If a downlink only traffic flow(s) is to be added the UE shall provide an UL packet filter that effectively disallows any useful packet flows (see clause 15.3.3.4 of TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7] for an example of such packet filter). NOTE 2: Receiving at least one UL packet filter from the UE ensures that a valid state for the TFT settings of the PDN connection as defined in clause 15.3.0 of TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7] is maintained if the TAD add operation results in the establishment of a new dedicated EPS bearer. If the UE wants to change the GBR in addition, the UE includes the GBR requirement of the EPS Bearer. The TAD is released when the procedure is completed. When only requesting for a modification of GBR (i.e. decrease or increase), the TAD shall include the existing packet filter identifier(s) for which the GBR change request applies to. The UE includes the GBR requirement of the EPS Bearer. The TAD is released when the procedure is completed. When requesting for a modification of packet filter(s) (e.g. change of port number), the TAD shall include packet filter identifier(s) for which the change request applies to together with the changed packet filter information. If the UE requests for deletion of traffic flows, the TAD includes the packet filter identifier(s) to be deleted. If the packet filters to be deleted were mapped to a GBR Bearer, the UE includes the new GBR requirement of the EPS Bearer. The UE sends the Linked Bearer Id (LBI) only when the requested operation is add, to indicate to which PDN connection the additional bearer resource is linked to. The EPS Bearer Identity is only sent when the requested operation is modify or delete. The Procedure Transaction Id is dynamically allocated by the UE for this procedure. The UE should ensure as far as possible that previously used PTI values are not immediately reused. The PTI is released when the procedure is completed. Protocol Configuration Options may be used to transfer application level parameters between the UE and the PDN GW (see TS 23.228[ IP Multimedia Subsystem (IMS); Stage 2 ]  [52]), and are sent transparently through the MME and the Serving GW. If the PDN GW indicated support for the 3GPP PS data off feature during PDN connection setup, the UE shall include in the PCO the 3GPP PS Data Off Support Indication, which indicates whether the user has activated or deactivated 3GPP PS Data Off. 2. The MME sends the Bearer Resource Command (IMSI, LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the selected Serving GW. The MME validates the request using the Linked Bearer Id. The same Serving GW address is used by the MME as for the EPS Bearer identified by the Linked Bearer Id received in the Request Bearer Resource Modification message. 3. The Serving GW sends the Bearer Resource Command (IMSI, LBI, PTI, EPS Bearer Identity, QoS, TAD, Protocol Configuration Options) message to the PDN GW. The Serving GW sends the message to the same PDN GW as for the EPS Bearer identified by the Linked Bearer Id. 4. The PDN GW may either apply a locally configured QoS policy, or it may interact with the PCRF to trigger the appropriate PCC decision, which may take into account subscription information. This corresponds to the beginning of a 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. When interacting with PCRF, the PDN GW provides to the PCRF the content of the TAD and, if applicable, the GBR change (increase or decrease) associated with the packet filter information contained in the TAD. The GBR change is either calculated from the current Bearer QoS and the requested Bearer QoS from the UE, or set to the requested GBR if the TAD indicates an add operation and no EPS Bearer Identity was received. If the TAD indicates an add operation, the requested QCI is also provided to the PCRF unless an existing packet filter identifier is provided together with the new packet filter. 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 the TAD operation is modify, delete, a request for changing the GBR, or add with a link to existing packet filter(s), then the PDN GW provides to the PCRF the SDF filter identifier(s), previously assigned on Gx, that correspond to the received packet filter identifiers of the EPS bearer indicated by the received EPS bearer identity. NOTE 3: The ability of the PCRF to handle multiple PCC rules in the same request depends on operator policy. It is therefore recommended that the UE avoids providing references to multiple packet filters for different applications and services. If the PDN GW detects that the 3GPP PS Data Off UE Status has changed, the PDN GW shall indicate this event to the charging system for offline and online charging. If the 3GPP PS Data Off UE Status indicates that 3GPP PS Data Off is activated for the UE, the PDN GW shall enforce the PCC rules for downlink traffic to be applied when 3GPP PS Data Off is activated, as described in TS 23.203[ Policy and charging control architecture ]  [6]. 5. If the request is accepted, either the Dedicated Bearer Activation Procedure (according to clause 5.4.1), the PDN GW Initiated Bearer Deactivation Procedure (according to clause 5.4.4.1) or one of the Bearer Modification Procedures (according to clause 5.4.2.1 or 5.4.3) is invoked. The PTI allocated by the UE is used as a parameter in the invoked Dedicated Bearer Activation Procedure, the PDN GW Initiated Bearer Deactivation Procedure or the Bearer Modification Procedure to correlate it to the UE Requested Bearer Resource Modification Procedure. This provides the UE with the necessary linkage to what EPS Bearer to be used for the new traffic flow aggregate. The PDN GW shall not modify the QoS parameters requested by the UE. The PDN GW inserts, modifies or removes packet filter(s) corresponding to the TAD into the TFT for the EPS bearer. If PCC is in use, the PDN GW uses the service data flow filters as specified in the resulting PCC rule(s). The PDN GW validates the state of the TFT settings of the PDN connection as defined in clause 15.3.0 of TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7]. If after the execution of all TAD operations the TFT of the dedicated EPS bearer contains only packet filters for the downlink direction, the PDN GW shall add a packet filter which effectively disallows any useful packet flows in uplink direction (see clause 15.3.3.4 in TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7] for an example of such a packet filter) to the TFT. NOTE 4: The PDN GW addition of an uplink packet filter allows the handling of pre-Release 11 UEs which may have provided only downlink packet filters in a TAD add operation without linking to an existing packet filter. When a new packet filter is inserted into a TFT, the PDN GW assigns a new packet filter identifier which is unique within the TFT. The PDN GW maintains the relation between the SDF filter identifier in the PCC rule received from the PCRF and the packet filter identifier of the TFT of this EPS bearer. If all of the packet filter(s) for a dedicated EPS bearer have been removed from the TFT, the PDN GW performs the PDN GW Initiated Bearer Deactivation Procedure. If the requested QoS is not granted (i.e. the requested QoS cannot be accepted or resources could not be allocated), or the resulting TFT settings of the PDN connection does not pass the validation, then the PDN GW sends a Bearer Resource Failure Indication (with a cause indicating the reason why the request failed or was rejected) message, which shall be delivered to the UE. 6. If the PDN GW interacted with the PCRF in step 4, the PDN GW indicates to the PCRF whether the PCC decision could be enforced or not. This corresponds to the completion of the PCEF-initiated IP-CAN session modification procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6], proceeding 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].