This procedure is triggered by the S-NG-RAN node to initiate the release of the resources for a specific UE.
The procedure uses UE-associated signalling.
The S-NG-RAN node initiates the procedure by sending the S-NODE RELEASE REQUIRED message to the M-NG-RAN node.
Upon reception of the S-NODE RELEASE REQUIRED message, the M-NG-RAN node replies with the S-NODE RELEASE CONFIRM message.
For each SN-terminated PDU session resource, the M-NG-RAN node may include the DL Forwarding UP Address IE and the UL Forwarding UP Address IE within the PDU Session Resources To Be Released Item IE to indicate that it requests data forwarding of uplink and downlink packets to be performed for that bearer.
The S-NG-RAN node may start data forwarding and stop providing user data to the UE upon reception of the S-NODE RELEASE CONFIRM message,
If the S-NODE RELEASE REQUIRED message contains an PDU session resource to be released which is configured with the SCG bearer option within the PDU sessions to be released List - SN terminated IE, the S-NG-RAN node shall include the RLC Mode IE within the DRBs To Be Released List IE in the PDU Session to be released List - SN terminated IE in the S-NODE RELEASE REQUIRED message. The RLC Mode IE indicates the RLC mode used in the S-NG-RAN node for the DRB.
If the S-NODE RELEASE CONFIRM message includes the DRB IDs taken into use IE, the S-NG-RAN node shall, if applicable, act as specified in TS 37.340
If the S-NG-RAN node to M-NG-RAN node Container IE is included in the S-NODE RELEASE REQUIRED message, the M-NG-RAN node may use the contained information to apply delta configuration.