The purpose of the gNB-CU-CP initiated BC Bearer Context Modification procedure is to allow the gNB-CU-CP to modify MBS session resources for a broadcast MBS session. The procedure uses MBS-associated signalling.
The gNB-CU-CP initiates the procedure by sending the BC BEARER CONTEXT MODIFICATION REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to perform at least partially the requested modifications it replies to the gNB-CU-CP with the BC BEARER CONTEXT MODIFICATION RESPONSE message.
The gNB-CU-UP shall report to the gNB-CU-CP, in the BC BEARER CONTEXT MODIFICATION RESPONSE message, the result of all the requested MBS session resources in the following way:
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A list of BC MRBs which are successfully established or modified shall be included in the BC MRB Setup or Modify Response List IE;
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A list of BC MRBs which failed to be established or modified shall be included in the BC MRB Failed List IE;
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For each newly established or modified BC MRB, a list of MBS QoS Flows which are successfully established or modified shall be included in the MBS QoS Flow Setup List IE;
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For each newly established or modified BC MRB, a list of MBS QoS Flows which failed to be established or modified shall be included in the MBS QoS Flow Failed List IE.
When the gNB-CU-UP reports the unsuccessful establishment of a BC MRB or MBS 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
BC Bearer Context NG-U TNL Info at 5GC To Setup or Modify IE is contained in the BC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the previously received BC Bearer Context NG-U TNL Info at 5GC.
If the gNB-CU-UP cannot successfully perform any of the requested modifications, it shall respond with a BC BEARER CONTEXT MODIFICATION FAILURE message and an appropriate cause value.
void.