o the core network elements such as the UPF (User Plane Function) and AMF (Access Management Function). Non-mobile 9 Transport network traffic is often carried by the same backbone: enterprise traffic, fixed residential Internet, and SO on. For 5G there is more variability in the use cases and in deployment options than ever before, and the location of the 5G network elements in the mobile backhaul tiers needs to be adapted SO that it fits the targeted use case, and vice versa, some functions on the mobile backhaul tiers may need to be placed deeper toward, or into the access tier. For example, low-latency applications require the core network function (UPF) to be located close to the UE, which can be supported by having the Mobile Edge Com- puting (MEC) function in the distribution or even in the access tier. For ultra-reliable communications, it may be necessary to have full resiliency already in the access tier and in the first mile access links, which in turn requires that the connectivity solu- tion in the access be capable of resilient service. A basic prerequisite for Ultra-Reliable Low-Latency Communication (URLLC), but essential for the non-URLLC case as well, is that failure domains be limited, failures contained, and the network kept in control under all circumstances. Every mobile transport network is a specific case, as the infrastructure on the current network often introduces some constraints or at a minimum provides a starting point for the 5G evolution. The intended target state may also differ. Many candidate technologies exist that may all be technically viable. Which alternative provides the best fit to the needs is very much case specific. 9.1.6 Logical and Physical Transport Topology Logical connectivity, which refers to which 5G mobile elements need connectivity with each other, is different from the physical transport topology. Logical connectivity needs to follow 3GPP definitions for the interfaces between the mobile network elements. The physical transmission topology is mostly irrelevan