Section: 8.9.9.1 Traffic Mapping from IP-layer to Layer-2
Content: When forwarding IP packets, the IAB-donor-DU performs the traffic mapping from IP-layer to layer-2 as defined in TS 38.340[ NR; Backhaul Adaptation Protocol (BAP) specification ]  [22]. The traffic mapping information is configured by the IAB-donor-CU, which contains the IP header information, and the BH information including the BAP routing ID and a list of egress link and BH RLC channel pairs. Multiple traffic mappings can contain the same BAP routing ID and/or list of egress link and BH RLC channel pairs. The traffic mappings can be configured as part of the UE Context Setup or UE Context Modification procedures. They may also be configured via the non-UE-associated BAP Mapping Configuration procedure. NOTE: Implementation must ensure the avoidance of potential race conditions, i.e. no conflicting configurations are concurrently performed using UE-associated and non-UE-associated procedures. The traffic mapping from IP-layer to layer-2 may include IPv6 Flow Label information. For DL F1 or X2 traffic, the IPv6 Flow Label information is set by the IAB-donor-CU or MeNB, respectively. When this traffic is protected via IPsec tunnel mode, the IPv6 Flow Label is set on the inner header by the IAB-donor-CU or MeNB, and the security gateway shall copy the IPv6 Flow Label from the inner IP header to the outer IP header to ensure that the IAB-donor-DU can perform the traffic mapping considering the IPv6 Flow Label. NOTE: Implementation must ensure that IPv6 Flow Label collisions are avoided on the IP backhaul network between security gateway and IAB-donor-DU.