Section: 5.3.9 Requirements for the gNB F1 interfaces
Content: Requirements given below apply to gNBs with split DU-CU implementations using F1 interface defined in TS 38.470[ NG-RAN; F1 general aspects and principles ]  [31]. Signalling traffic (i.e. both F1-C interface management traffic defined in TS 38.470[ NG-RAN; F1 general aspects and principles ]  [31] and F1-C signalling bearer defined in TS 38.472[ NG-RAN; F1 signalling transport ]  [32]) and user plane data can be sent on the F1 interface between a given DU and its CU. - F1-C interface shall support confidentiality, integrity and replay protection. - All management traffic carried over the CU-DU link shall be integrity, confidentiality and replay protected. - The gNB shall support confidentiality, integrity and replay protection on the gNB DU-CU F1-U interface [33] for user plane. - F1-C and management traffic carried over the CU-DU link shall be protected independently from F1-U traffic. NOTE: The above requirements allow to have F1-U protected differently (including turning integrity and/or encryption off or on for F1-U) from all other traffic on the CU-DU (e.g. the traffic over F1-C).