The present document specifies the standards for user data transport protocols and related signalling protocols to establish user plane transport bearers over the F1 interface. The F1 interface provides means for interconnecting a gNBCU and a gNB-DU of a gNB within an NG-RAN@ or for interconnection a gNB-CU and a gNB-DU of an en-gNB within an E-UTRAN.