Figure 6.1.4-1 shows the protocol stack for F1-U between IAB-DU and the IAB-donor-CU-UP, and Figure 6.1.4-2 shows the protocol stack for F1-C between IAB-DU and the IAB-donor-CU-CP. In these example Figures, F1-U and F1-C traffic are carried over two backhaul hops.