Content for  TS 37.483  Word version:  18.2.0

The purpose of the MC Bearer Context Setup procedure is to allow the gNB-CU-CP to establish MBS session resources for a multicast MBS session in the gNB-CU-UP. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the MC BEARER CONTEXT SETUP REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to establish the requested MBS session resources, it replies to the gNB-CU-CP with the MC BEARER CONTEXT SETUP RESPONSE message. If MRB resources are requested to be setup by the gNB-CU-CP the gNB-CU-UP shall report to the gNB-CU-CP, in the MC BEARER CONTEXT SETUP RESPONSE message, the result of all the requested resources in the following way:

• A list of MC MRBs which are successfully established shall be included in the MC MRB Setup Response List IE;
• A list of MC MRBs which failed to be established shall be included in the MC MRB Failed List IE;
• For each established MC MRB, a list of MBS QoS Flows which are successfully established shall be included in the MBS QoS Flow Setup List IE;
• For each established MC MRB, a list of MBS QoS Flows which failed to be established shall be included in the MBS QoS Flow Failed List IE.

When the gNB-CU-UP reports the unsuccessful establishment of a MC 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 MRB resources are requested to be setup by the gNB-CU-CP and if the Requested Action for Available Shared NG-U Termination IE in the MC Bearer Context To Setup IE in the MC BEARER CONTEXT SETUP REQUEST message is set to

• "apply available configuration" and an appropriate Shared NG-U Termination is available, the gNB-CU-UP shall apply the radio bearer configuration of the Shared NG-U Termination, and indicate in the MC BEARER CONTEXT SETUP RESPONSE message within the Available MC MRB Configuration IE in the MC Bearer Context To Setup Response IE the radio bearer configuration of the Shared NG-U Termination, if the radio bearer configuration of the Shared NG-U Termination is different than the one requested by the gNB-CU-CP.
• "apply requested configuration" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination if the radio bearer configuration of the Shared NG-U Termination, is the same as the one requested by the gNB-CU-CP, otherwise allocate separate resources as requested by the gNB-CU-CP and indicate in the MC BEARER CONTEXT SETUP RESPONSE message within the Available MC MRB Configuration IE in the MC Bearer Context To Setup Response IE the radio bearer configuration of the Shared NG-U Termination.
• "apply available configuration if same as requested" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination only if the radio bearer configuration of the Shared NG-U Termination is the same as the one requested by the gNB-CU-CP and reply with MC BEARER CONTEXT SETUP RESPONSE message.

If the MBS Session Associated Information Non-Support-to-Support IE is contained in the MC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall, if supported, perform duplication elimination between the packets delivered through the individual NG-U tunnel and the shared NG-U tunnel. If the MBS Area Session ID IE is received in the MC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall, if supported, store it and use it to establish the shared NG-U tunnel. If the MC Bearer Context Status Change IE set to "Resume" is contained in the MC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall, if supported, resume transmitting DL data. Interaction with other procedures If the MC Bearer Context Status Change IE is contained in the MC BEARER CONTEXT SETUP REQUEST message and set to "Suspend", the gNB-CU-UP shall, if supported,

• suspend transmitting DL data to the gNB-DU.
• upon DL data arrival, buffer the received DL data and trigger the MC Bearer Notification procedure to indicate DL Data Arrival to the gNB-CU-CP.

If the MC Bearer Context Inactivity Timer IE is contained in MC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall take it into account when performing inactivity monitoring, and if applicable, trigger MC Bearer Notification procedure to indicate inactivity of the MC Bearer context to the gNB-CU-CP.

If the gNB-CU-UP cannot establish the requested MBS session resources for the multicast MBS session, it shall consider the procedure as failed and respond with the MC BEARER CONTEXT SETUP FAILURE message and an appropriate cause value. If the Requested Action for Available Shared NG-U Termination IE in the MC Bearer Context To Setup IE in the MC BEARER CONTEXT SETUP REQUEST message is set to "apply available configuration if same as requested" and the requested configuration does not match the available shared NG-U termination, the gNB-CU UP shall reply with MC BEARER CONTEXT SETUP FAILURE message.

void.

The purpose of the gNB-CU-CP initiated MC Bearer Context Modification procedure is to allow the gNB-CU-CP to modify MBS session resources for a multicast MBS session. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the MC 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 MC BEARER CONTEXT MODIFICATION RESPONSE message. If MRB resources are requested to be setup or modified by the gNB-CU-CP, the gNB-CU-UP shall report to the gNB-CU-CP, in the MC BEARER CONTEXT MODIFICATION RESPONSE message, the result of all the requested resources in the following way:

• A list of MC MRBs which are successfully established or modified shall be included in the MC MRB Setup or Modify Response List IE;
• A list of MC MRBs which failed to be established or modified shall be included in the MC MRB Failed List IE;
• For each newly established or modified MC MRB, a list of MBS QoS Flows which are successfully established or modified shall be included in the MBS QoS Flow Setup List IE;
• For each newly established or modified MC 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 MC 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 MRB resources are requested to be setup by the gNB-CU-CP and if the Requested Action for Available Shared NG-U Termination IE in the MC Bearer Context To Modify IE in the MC BEARER CONTEXT MODIFICATION REQUEST message is set to

• "apply available configuration" and an appropriate Shared NG-U Termination is available, the gNB-CU-UP shall apply the radio bearer configuration of the Shared NG-U Termination, and indicate in the MC BEARER CONTEXT MODIFICATION RESPONSE message within the Available MC MRB Configuration IE in the MC Bearer Context To Modify Response IE the radio bearer configuration of the Shared NG-U Termination, if the radio bearer configuration of the Shared NG-U Termination is different than the one requested by the gNB-CU-CP.
• "apply requested configuration" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination if the radio bearer configuration of the Shared NG-U Termination, is the same as the one requested by the gNB-CU-CP, otherwise allocate separate resources as requested by the gNB-CU-CP and indicate in the MC BEARER CONTEXT MODIFICATION RESPONSE message within the Available MC MRB Configuration IE in the MC Bearer Context To Modify Response IE the radio bearer configuration of the Shared NG-U Termination.
• "apply available configuration if same as requested" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination only if the radio bearer configuration of the Shared NG-U Termination is the same as the one requested by the gNB-CU-CP and reply with MC BEARER CONTEXT MODIFICATION RESPONSE message.

If the MC Bearer Context NG-U TNL Info at 5GC IE is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the previously received MC Bearer Context NG-U TNL Info at 5GC. If the MC Bearer Context NG-U TNL Info at NG-RAN Request IE is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall include the MC Bearer Context NG-U TNL Info at NG-RAN Modify Response IE in the MC BEARER CONTEXT MODIFICATION RESPONSE message. If the MRB Progress Information Request Type IE is contained within the MC Forwarding Resource Request IE in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, include the requested information in the MRB Progress Information IE within the MC Forwarding Resource Response IE in the MC BEARER CONTEXT MODIFICATION RESPONSE message. If the MRB Forwarding Address Request IE set to "true" is contained in the MC Forwarding Resource Request IE in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, include the MRB Forwarding Address IE within the MC Forwarding Resource Response IE in the MC BEARER CONTEXT MODIFICATION RESPONSE message. If the MC Forwarding Resource Indication IE is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, take the included information into account. If the MC Forwarding Resource Release IE is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, release the indicated MC Forwarding Resource. If the MBS Session Associated Information Non-Support-to-Support IE is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, perform duplication elimination between the packets delivered through the individual NG-U tunnel and the shared NG-U tunnel. If the MC Bearer Context Status Change IE set to "Resume" is contained in the MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall, if supported, resume transmitting DL data. Interaction with other procedures If the MC Bearer Context Status Change IE is contained in MC BEARER CONTEXT MODIFICATION REQUEST message and set to "Suspend", the gNB-CU-UP shall, if supported,

• suspend transmitting DL data to the gNB-DU.
• upon DL data arrival, buffer the received DL data and trigger the MC Bearer Notification procedure to indicate DL Data Arrival to the gNB-CU-CP.

If the MC Bearer Context Inactivity Timer IE is contained in MC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall take it into account when perform inactivity monitoring, and if applicable, trigger MC Bearer Notification procedure to indicate inactivity of the MC Bearer context to the gNB-CU-CP.

If the gNB-CU-UP cannot successfully perform any of the requested modifications, it shall respond with a MC BEARER CONTEXT MODIFICATION FAILURE message and an appropriate cause value. If the Requested Action for Available Shared NG-U Termination IE in the MC Bearer Context To Setup IE in the MC BEARER CONTEXT MODIFICATION REQUEST message is set to "apply available configuration if same as requested" and the requested configuration does not match the available shared NG-U termination, the gNB-CU UP shall reply with MC BEARER CONTEXT MODIFICATION FAILURE message.

void.

The purpose of the gNB-CU-UP initiated MC Bearer Context Modification Required procedure is to allow the gNB-CU-UP to request the gNB-CU-CP to initiate the modification of MBS session resources for a multicast MBS session and inform the gNB-CU-CP. The procedure uses MBS-associated signalling.

The gNB-CU-UP initiates the procedure by sending the MC BEARER CONTEXT MODIFICATION REQUIRED message to the gNB-CU-CP. The gNB-CU-CP replies to the gNB-CU-UP with the MC BEARER CONTEXT MODIFICATION CONFIRM message. If the MC Forwarding Resource Release Indication IE is contained in the MC BEARER CONTEXT MODIFICATION REQUIRED message, the gNB-CU-CP shall, if supported, assume that the indicated MC Forwarding Resource was released by the gNB-CU-UP.

Void.

The purpose of the gNB-CU-CP initiated MC Bearer Context Release procedure is to allow the gNB-CU-CP to command the release of MBS session resources for a multicast MBS Session. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the MC BEARER CONTEXT RELEASE COMMAND message to the gNB-CU-UP. Upon reception of the MC BEARER CONTEXT RELEASE COMMAND message, the gNB-CU-UP shall release all related signalling and user data transport resources and reply with the MC BEARER CONTEXT RELEASE COMPLETE message.

Not applicable.

The purpose of the MC Bearer Context Release Request procedure is to allow the gNB-CU-UP to request the gNB-CU-CP to trigger the release of MBS session resources for a multicast MBS Session. The procedure uses MBS-associated signalling.

The gNB-CU-UP initiates the procedure by sending the MC BEARER CONTEXT RELEASE REQUEST message to the gNB-CU-CP. Interactions with gNB-CU-CP initiated MC Bearer Context Release procedure: Upon reception of the MC BEARER CONTEXT RELEASE REQUEST message the gNB-CU-CP should initiate the MC Bearer Context Release procedure.

Not applicable.

The purpose of MC Bearer Notification procedure is initiated by the gNB-CU-UP to indicate DL data arrival or inactivity of the MC Bearer context. The procedure uses MBS-associated signalling.

The gNB-CU-UP initiates the procedure by sending the MC BEARER NOTIFICATION message to the gNB-CU-CP.

Not applicable.