Section: 8.8 Multiple TNLAs for F1-C
Content: In the following, the procedure for managing multiple TNLAs for F1-C is described. Figure 8.8-1: Managing multiple TNLAs for F1-C. 1. The gNB-DU establishes the first TNLA with the gNB-CU using a configured TNL address. NOTE: The gNB-DU may use different source and/or destination IP end point(s) if the TNL establishment towards one IP end point fails. How the gNB-DU gets the remote IP end point(s) and its own IP address are outside the scope of this specification. 2-3. Once the TNLA has been established, the gNB-DU initiates the F1 Setup procedure to exchange application level configuration data. 4-6. The gNB-CU may add additional TNL Endpoint(s) to be used for F1-C signalling between the gNB-CU and the gNB-DU pair using the gNB-CU Configuration Update procedure. The gNB-CU Configuration Update procedure also allows the gNB-CU to request the gNB-DU to modify or release TNLA(s). 7-9. The gNB-DU may add additional TNL association(s) to be used for F1-C signalling using a gNB-CU endpoint already in use for existing TNL associations between the gNB-CU and the gNB-DU pair. The gNB-DU CONFIGURATION UPDATE message including the gNB-DU ID shall be the first F1AP message sent on an additional TNLA of an already setup F1-C interface instance after the TNL association has become operational. The F1AP UE TNLA binding is a binding between a F1AP UE association and a specific TNL association for a given UE. After the F1AP UE TNLA binding is created, the gNB-CU can update the UE TNLA binding by sending the F1AP message for the UE to the gNB-DU via a different TNLA. The gNB-DU shall update the F1AP UE TNLA binding with the new TNLA. The gNB-DU Configuration Update procedure also allows the gNB-DU to inform the gNB-CU that the indicated TNLA(s) will be removed by the gNB-DU.