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Content for  TS 38.463  Word version:  16.3.0

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8.3.2  Bearer Context Modification (gNB-CU-CP initiated)

8.3.2.1  General

The purpose of the Bearer Context Modification procedure is to allow the gNB-CU-CP to modify a bearer context in the gNB-CU-UP. The procedure uses UE-associated signalling.

8.3.2.2  Successful OperationWord‑p. 35
Reproduction of 3GPP TS 38.463, Figure 8.3.2.2-1: Bearer Context Modification procedure: Successful Operation.
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The gNB-CU-CP initiates the procedure by sending the BEARER CONTEXT MODIFICATION REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to modify the bearer context, it replies to the gNB-CU-CP with the BEARER CONTEXT MODIFICATION RESPONSE message.
The gNB-CU-UP shall report to the gNB-CU-CP, in the BEARER CONTEXT MODIFICATION RESPONSE message, the result for all the requested resources in the following way:
  • For E-UTRAN:
    • A list of DRBs which are successfully established shall be included in the DRB Setup List IE;
    • A list of DRBs which failed to be established shall be included in the DRB Failed List IE;
    • A list of DRBs which are successfully modified shall be included in the DRB Modified List IE;
    • A list of DRBs which failed to be modified shall be included in the DRB Failed To Modify List IE;
  • For NG-RAN:
    • A list of PDU Session Resources which are successfully established shall be included in the PDU Session Resource Setup List IE;
    • A list of PDU Session Resources which failed to be established shall be included in the PDU Session Resource Failed List IE;
    • A list of PDU Session Resources which are successfully modified shall be included in the PDU Session Resource Modified List IE;
    • A list of PDU Session Resources which failed to be modified shall be included in the PDU Session Resource Failed To Modify List IE;
    • For each successfully established or modified PDU Session Resource, a list of DRBs which are successfully established shall be included in the DRB Setup List IE;
    • For each successfully established or modified PDU Session Resource, a list of DRBs which failed to be established shall be included in the DRB Failed List IE;
    • For each successfully modified PDU Session Resource, a list of DRBs which are successfully modified shall be included in the DRB Modified List IE;
    • For each successfully modified PDU Session Resource, a list of DRBs which failed to be modified shall be included in the DRB Failed To Modify List IE;
    • For each successfully established or modified DRB, a list of QoS Flows which are successfully established shall be included in the Flow Setup List IE;
    • For each successfully established or modified DRB, a list of QoS Flows which failed to be established shall be included in the Flow Failed List IE;
When the gNB-CU-UP reports the unsuccessful establishment of a PDU Session Resource, DRB or QoS Flow the cause value should be precise enough to enable the gNB-CU-CP to know the reason for the unsuccessful establishment.
If the Security Information IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the UE DL Aggregate Maximum Bit Rate IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the UE DL Maximum Integrity Protected Data Rate IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the Bearer Context Status Change IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall consider the UE RRC state and act as specified in TS 38.401.
If the Data Forwarding Information Request IE, PDU Session Data Forwarding Information Request IE or the DRB Data Forwarding Information Request IE are included in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall include the requested forwarding information in the Data Forwarding Information Response IE, PDU Session Data Forwarding Information Response IE or the DRB Data Forwarding Information Response IE in the BEARER CONTEXT MODIFICATION RESPONSE message.
If the PDCP Configuration IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information, except for the PDCP SN UL Size IE, the PDCP SN DL Size IE and the RLC mode IE which shall be ignored.
If the E-UTRAN QoS IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the PDCP SN Status Request IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall act as specified in TS 38.401 and include the UL COUNT Value IE and the DL COUNT Value IE in the BEARER CONTEXT MODIFICATION RESPONSE message.
If the PDCP SN Status Information IE is contained in the DRB To Setup List IE or the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall take it into account and act as specified in TS 38.401.
If the DL UP Parameters IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the Cell Group To Add IE or the Cell Group To Modify IE or the Cell Group To Remove IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall add or modify or remove the corresponding cell group.
If the PDU Session Resource DL Aggregate Maximum Bit Rate IE is contained in the PDU Session Resource To Setup List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall replace the information in the UE context and use it when enforcing downlink traffic policing for the non GBR QoS flows for the concerned UE, as specified in TS 23.501.
If the PDU Session Resource DL Aggregate Maximum Bit Rate IE is contained in the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the SDAP Configuration IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
If the Flow Mapping Information IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the corresponding information.
For each requested DRB, if the PDCP Duplication IE or Additional PDCP duplication Information IE is included in the PDCP Configuration IE contained in the BEARER CONTEXT MODIFICATION REQUEST message, and one cell group is included in Cell Group Information IE, then the gNB-CU-CP shall include two or more UP Transport Layer Information IEs in the BEARER CONTEXT MODIFICATION REQUEST message, and the gNB-CU-UP shall also include two or more UP Transport Layer Information IEs in the BEARER CONTEXT MODIFICATION RESPONSE message to support packet duplication for intra-gNB-DU CA. The first UP Transport Layer Information IE of these UP Transport Layer Information IEs is for the primary path.
If more than one cell group is included in the Cell Group Information IE, then the gNB-CU-UP shall consider that the request concerns for DC-based packet duplication where the number of duplication tunnels for each cell group is indicated by the Number of tunnels IE, and that the first UP Transport Layer Information IE for each cell group is for the primary path or the split secondary path.
For a certain DRB which was allocated with two or more GTP-U tunnels, if such DRB is modified and given one GTP-U tunnel via the Bearer Context Modification (gNB-CU-CP initiated) procedure, i.e. only one UP Transport Layer Information per Cell Group ID is present in DL UP Parameters IE for the concerned DRB, then the gNB-CU-UP shall consider that PDCP duplication is deconfigured for this DRB. If such Bearer Context Modification (gNB-CU-CP initiated) procedure occurs, the Duplication Activation IE shall not be included for the concerned DRB.
If the New UL TNL Information Required IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall include the new UP Transport Layer Information in the BEARER CONTEXT MODIFICATION RESPONSE message.
For each PDU session for which the Security Indication IE is included in the PDU Session Resource To Setup List IE of the BEARER CONTEXT MODIFICATION REQUEST message, and the Integrity Protection Indication IE or Confidentiality Protection Indication IE is set to "preferred", then the gNB-CU-UP should, if supported, perform user plane integrity protection or ciphering, respectively, for the concerned PDU session and shall notify whether it performed the user plane integrity protection or ciphering by including the Integrity Protection Result IE or Confidentiality Protection Result IE, respectively, in the PDU Session Resource Setup List IE of the BEARER CONTEXT MODIFICATION RESPONSE message.
For each PDU session for which the Security Indication IE is included in the PDU Session Resource To Setup List IE of the BEARER CONTEXT MODIFICATION REQUEST message, and the Integrity Protection Indication IE or Confidentiality Protection Indication IE is set to "required", then the gNB-CU-UP shall perform user plane integrity protection or ciphering, respectively, for the concerned PDU Session. If the gNB-CU-UP cannot perform the user plane integrity protection or ciphering, it shall reject the setup of the PDU Session Resources with an appropriate cause value.
For each PDU session for which the Security Indication IE is included in the PDU Session Resource To Setup List of the BEARER CONTEXT MODIFICATION REQUEST message:
  • if the Integrity Protection Indication IE is set to "not needed", then the gNB-CU-UP shall not perform user plane integrity protection for the concerned PDU session;
  • if the Confidentiality Protection Indication IE is set to "not needed", then the gNB-CU-UP shall not perform user plane ciphering for the concerned PDU session.
For each PDU Session Resource, if the Network Instance IE is included in the PDU Session Resource To Setup List IE or the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message and the Common Network Instance IE is not included, the gNB-CU-UP shall, if supported, use it when selecting transport network resource as specified in TS 23.501.
For each PDU session, if the Common Network Instance IE is included in the PDU Session Resource To Setup List IE or the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, use it when selecting transport network resource as specified in TS 23.501.
For each PDU session, if the Redundant NG UL UP Transport Layer Information IE is included in the PDU Session Resource To Setup List IE or the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, include the Redundant NG DL UP Transport Layer Information IE in the PDU Session Resource Setup List IE or the PDU Session Resource Modified List IE in the BEARER CONTEXT MODIFICATION RESPONSE message.
If the Redundant Common Network Instance IE is included in the PDU Session Resource To Setup List IE or the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, use it when selecting transport network resource for the redundant transmission as specified in TS 23.501.
For each PDU session for which the Redundant QoS Flow Indicator IE is included in QoS Flows Information To Be Setup IE contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if support, shall store and use it as specified in TS 23.501.
For each PDU session, if the Redundant QoS Flow Indicator IE is set to false for all QoS flows, the gNB-CU-UP shall, if supported, stop the redundant transmission and release the redundant tunnel for the concerned PDU session as specified in TS 23.501.
If the QoS Flow Mapping Indication IE is contained in the QoS Flow QoS Parameters List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, replace any previously received value and take it into account that only the uplink or downlink QoS flow is mapped to the DRB.
If the Data Discard Required IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message and the value is set to "Required", the gNB-CU-UP shall consider that a RAN Paging Failure occurred for that UE. The gNB-CU-UP shall discard the user plane data for that UE and consider that the bearer context is still suspended.
If UE Inactivity Timer IE or PDU session Inactivity Timer IE or DRB Inactivity Timer IE is contained in BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall take it into account when perform inactivity monitoring.
If the S-NSSAI IE is contained in the PDU Session Resource To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall store the corresponding information and replace any existing information.
If the DRB QoS IE is contained within the DRB To Setup List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, take it into account for each DRB, as specified in TS 28.552.
If the DRB QoS IE is contained within the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, replace any previously received value and take it into account for each DRB, as specifed in TS 28.552.
If the gNB-DU-ID IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall store and replace any previous information received.
If the RAN UE ID IE is contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall store and replace any previous information received.
If the gNB-CU-UP receives a BEARER CONTEXT MODIFICATION REQUEST message including Activity Notification Level IE and its value does not match the current bearer context, the gNB-CU-UP shall ignore the Activity Notification Level IE and also the requested modification of inactivity timer.
For each successfully established DRB, the gNB-CU-UP shall provide, in the respective UL UP Parameters IE of the BEARER CONTEXT MODIFICATION RESPONSE, one UL UP Transport Layer Information Item per cell group entry contained in the respective Cell Group Information IE of the BEARER CONTEXT MODIFICATION REQUEST message.
If the Old QoS Flow List - UL End Marker expected IE is included in the PDU Session Resource To Modify List IE of the BEARER CONTEXT MODIFICATION REQUEST message for a DRB to be modified, the gNB-CU-UP shall consider that the source NG-RAN node has initiated QoS flow re-mapping and has not yet received SDAP end markers, as described in TS 38.300. The gNB-CU-UP shall consider that the Old QoS Flow List - UL End Marker expected IE only contains UL QoS flow information for QoS flows for which no SDAP end marker has been yet received on the source side.
For EN-DC, if the Subscriber Profile ID for RAT/Frequency priority IE is included in the BEARER CONTEXT MODIFICATION REQUEST, the gNB-CU-UP may use it to apply specific RRM policies as specified in TS 36.300. If the Additional RRM Policy Index IE is included in the BEARER CONTEXT MODIFICATION REQUEST, the gNB-CU-UP may use it to apply specific RRM policies as specified in TS 36.300.
If there is at least one DRB removed by the gNB-CU-UP, the gNB-CU-UP shall, if supported, include the Retainability Measurements Information IE in the BEARER CONTEXT MODIFICATION RESPONSE message, providing information on the removed DRB(s) for retainability measurements in the gNB-CU-CP, as described in TS 32.425 and TS 28.552.
If the TSC Traffic Characteristics IE is included in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, take into account the corresponding information received in the TSC Traffic Characteristics IE.
For each QoS flow whose DRB has been successfully established or modified and the QoS Monitoring Request IE was included in the QoS Flow Level QoS Parameters IE contained in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall store this information, and, if supported, perform delay measurement and QoS monitoring, as specified in TS 23.501.
For each requested DRB, if the QoS Mapping Information IE is contained in the DL UP Parameters IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall use it to set DSCP and/or flow label fields in the downlink IP packets which are transmitted through the GTP tunnels indicated by the UP Transport Layer Information IE.
If the Early Forwarding COUNT Request IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall act as specified in TS 38.401 and include the requested FIRST DL COUNT Value IE or DISCARD DL COUNT Value IE in the BEARER CONTEXT MODIFICATION RESPONSE message.
If the Early Forwarding COUNT Information IE is contained in the DRB To Modify List IE in the BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall take it into account and act as specified in TS 38.401.
Interaction with the Bearer Context Modification (gNB-CU-CP initiated)
If the BEARER CONTEXT MODIFICATION REQUEST message includes for a DRB in the DRB To Modify List IE the PDCP SN Status Request IE set to "requested" and if the gNB-CU-UP has not yet received a SDAP end marker packet for a QoS flow which has been previously re-configured to another DRB by means of a gNB-CU-CP initiated Bearer Context Modification procedure, the gNB-CU-UP shall includes the QoS Flow Identifier of that QoS flow in the Old QoS Flow List - UL End Marker expected IE in the PDU Session Resource Modified List IE in the BEARER CONTEXT MODIFICATION RESPONSE message.
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8.3.2.3  Unsuccessful OperationWord‑p. 39
Reproduction of 3GPP TS 38.463, Figure 8.3.2.3-1: Bearer Context Modification procedure: Unsuccessful Operation.
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If the gNB-CU-UP cannot successfully perform any of the requested bearer context modifications, it shall respond with a BEARER CONTEXT MODIFICATION FAILURE message and appropriate cause value.

8.3.2.4  Abnormal Conditions

If the gNB-CU-UP receives a BEARER CONTEXT MODIFICATION REQUEST message containing a E-UTRAN QoS IE in the DRB To Setup List or the DRB To Modify List IE for a GBR QoS DRB but where the GBR QoS Information IE is not present, the gNB-CU-UP shall report the addition or the modification of the corresponding DRB as failed in the DRB Failed List IE or the DRB Failed To Modify List IE of the BEARER CONTEXT MODIFICATION RESPONSE message with an appropriate cause value.
If the gNB-CU-UP receives a BEARER CONTEXT MODIFICATION REQUEST message containing a QoS Flow Level QoS Parameters IE in the PDU Session Resource To Setup List IE or the PDU Session Resource To Modify List IE for a GBR QoS Flow but where the GBR QoS Flow Information IE is not present, the gNB-CU-UP shall report the addition or the modification of the corresponding QoS Flow as failed in the corresponding Flow Failed List IE of the BEARER CONTEXT MODIFICATION RESPONSE message with an appropriate cause value.
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