Section: 8.4.2.1 EN-DC
Content: This clause gives the SgNB release procedure in EN-DC given that the en-gNB consists of a gNB-CU and gNB-DU(s). MN initiated SN Release Figure 8.4.2.1-1 SgNB release procedure in EN-DC (MN initiated) 1~8: refer to TS 37.340[ Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Overall Description; Stage-2 ]  [12]. NOTE: The timing of sending the Step 2 SGNB RELEASE REQUEST ACKNOWLEDGE message is an example, it may be sent e.g. after step a1 or after a2 and it is up to implementation. a1. After receiving SGNB RELEASE REQUEST message from MeNB, gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message to gNB-DU to stop the data transmission for the UE. It is up to gNB-DU implementation when to stop the UE scheduling. a2. gNB-DU responds to gNB-CU with UE CONTEXT MODIFICATION RESPONSE message. a3. After receiving the UE CONTEXT RELEASE message from MeNB, the gNB-CU sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU to release the UE context. a4. The gNB-DU responds to the gNB-CU with the UE CONTEXT RELEASE COMPLETE message. SN initiated SN Release Figure 8.4.2.1-2 SgNB release procedure in EN-DC (SN initiated) 1~8: refer to TS 37.340[ Evolved Universal Terrestrial Radio Access (E-UTRA) and NR; Multi-connectivity; Overall Description; Stage-2 ]  [12]. a1. gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message to gNB-DU to stop the data transmission for the UE. It is up to gNB-DU implementation when to stop the UE scheduling. This step may occur before step 1. a2. gNB-DU responds to gNB-CU with UE CONTEXT MODIFICATION RESPONSE message. a3. After receiving the UE CONTEXT RELEASE message from MeNB, the gNB-CU sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU to release the UE context. a4. The gNB-DU responds to the gNB-CU with the UE CONTEXT RELEASE COMPLETE message.