time constraint required by the targeted service, divided by the total number of sent network layer packets" [24]. Reliability is thus not equivalent to availability. The first mile transport link availability in a traditional macro transport network is planned, for example, for four nines (99.99%), still allowing for 52 min of outage in a year. What helps is that radio network cells often 9 Transport partly overlap and service is not lost even when an individual site or the access link fails. Access links are seldom duplicated. For recovery, protection switching or restoration may be utilized, or a combination of the two, for example, with IP and optical services. Replicated signals or packet streams (1 + 1 type of protection) enable the receiving end to select the signal from the working path at any time. A number of solutions exist (mobile backhaul related in [25]), which can be considered for URLLC transport. Specifically with respect to URLLC, in a 5G radio network, dual (or multi) connectivity to the terminal is studied in 3GPP, with packet stream duplication at the PDCP layer [26]. See Section 7.4.6 in Chapter 7 for PDCP layer duplication. Since the PDCP layer terminates at the gNB (or gNB-CU), this packet duplication also covers the F1 and Xn transport links. Underlying transport services are then designed for sufficient transport layer availability taking into account the possible higher layer replication, SO that the system target is met. IEEE TSN proposes multiple enhancements to the local area bridging standards, for example, replication of streams over multiple disjoint paths [27]. The deterministic net- works working group of IETF addresses the same field but more from the IP networking standpoint, in collaboration with IEEE. 9.5.3 IAB (Integrated Access and Backhaul) Provisioning the first mile access link to the base station is in many cases difficult. Fiber may not necessarily be available right at the desired location, even when it is available in a cable conduit underground. Using a separate wi