Section: M.3 IAB-node Integration Procedure M.3.1 General
Content: IAB-node, consists of a UE function (referred to as IAB-UE) and gNB-DU function [2]. IAB integration procedure consists of 3 phases detailed in TS 38.401[ NG-RAN; Architecture description ]  [78]. Phase-1: IAB-UE part setup: The IAB-UE performs registration procedure to the network as a UE as described in TS 23.501[ System architecture for the 5G System (5GS) ]  [2] and TS 23.502[ Procedures for the 5G System (5GS) ]  [8] in order to register to the 5GC and consequently, the NAS and AS security are established between the IAB-node and 5GC. Phase-2: BH RLC channel establishment and routing update: The BH RLC channels and the BAP layer are established and configured in the IAB-node by the IAB-donor using the secured RRC signalling to support routing between the IAB-node and the IAB-donor. Phase-3: gNB -DU part setup: F1 security establishment for IAB is performed over the RLC channel. The Phase-1 results in IAB-UE registration and consequently, AS security establishment between the IAB donor and IAB-node, Phase-2 results in configuration of the IAB-node securely using the established AS security and Phase-3 results in the establishment of secure F1 interface between the IAB-donor and IAB-node.