Section: 6.1.2 Overall architecture for separation of gNB-CU-CP and gNB-CU-UP
Content: The overall architecture for separation of gNB-CU-CP and gNB-CU-UP is depicted in Figure 6.1.2-1. NOTE: NG-RAN could also consist of a set of ng-eNBs, an ng-eNB may consist of an ng-eNB-CU-CP, one or more ng-eNB-CU-UP(s), and one or more ng-eNB-DU(s). An ng-eNB-CU-CP and an ng-eNB-CU-UP is connected via the E1 interface. An ng-eNB-DU is connected to an ng-eNB-CU-CP via the W1-C interface, and to an ng-eNB-CU-UP via the W1-U interface. The general principle described in this clause also applies to ng-eNB and its corresponding E1 and W1 interfaces, if not explicitly specified otherwise. Figure 6.1.2-1. Overall architecture for separation of gNB-CU-CP and gNB-CU-UP - A gNB may consist of a gNB-CU-CP, multiple gNB-CU-UPs and multiple gNB-DUs; - The gNB-CU-CP is connected to the gNB-DU through the F1-C interface; - The gNB-CU-UP is connected to the gNB-DU through the F1-U interface; - The gNB-CU-UP is connected to the gNB-CU-CP through the E1 interface; - One gNB-DU is connected to only one gNB-CU-CP; - One gNB-CU-UP is connected to only one gNB-CU-CP; NOTE 1: For resiliency, a gNB-DU and/or a gNB-CU-UP may be connected to multiple gNB-CU-CPs by appropriate implementation. - One gNB-DU can be connected to multiple gNB-CU-UPs under the control of the same gNB-CU-CP; - One gNB-CU-UP can be connected to multiple DUs under the control of the same gNB-CU-CP; NOTE 2: The connectivity between a gNB-CU-UP and a gNB-DU is established by the gNB-CU-CP using Bearer Context Management functions. NOTE 3: The gNB-CU-CP selects the appropriate gNB-CU-UP(s) for the requested services for the UE. In case of multiple CU-UPs they belong to same security domain as defined in TS 33.210[ Network Domain Security (NDS); IP network layer security ]  [18]. NOTE 4: Data forwarding between gNB-CU-UPs during intra-gNB-CU-CP handover within a gNB may be supported by Xn-U.