twork deployment models and practices based on traditional backhaul or fronthaul requirements are likely to be unsustainable and expensive for 5G deployments as the need for integrated access and backhaul in heterogeneous networks becomes more compelling. The NGFI is the new 5G Network Architecture Leaf access network Metro network- Backhauk EPC/5GC ((1)")) Split option X Split option y NGFI-I NGFI-II- EPC/5GC Transport sub networks Figure 1.36 Example of RAN aggregation node with CU and DUs 78]. packet-based fronthaul interface specified by IEEE 1914.1 47 in order to provide bandwidth efficiency and to achieve scalability in transport networks as the CPRI standard cannot scale with the bandwidth requirements of 5G. IEEE 1914.1 standard simplifies network design and operation, increases network flexibility and resource utilization, and lowers cost by leveraging the existing and mature Ethernet-based solutions for critical functions such as QoS, synchronization, and data security. The fronthaul architecture provides unified man- agement and control mechanisms, common networking protocols, and universal network elements, thus facilitating migration to cloud-based mobile networks. As shown in Fig. 1.36, the high-level architecture for transport network for the next- generation mobile systems is typically hierarchical and rigorously follows the physical OTN topology. In the reference architecture, the core network is where the packet core gateways are located. The metro aggregation network aggregates one or more metro ANs, which again aggregates one or more cell site or leaf transport networks. Ring network topologies are common due to their resilience properties; however, other topologies are also conceiv- able. The leaf networks are often point-to-point topologies. There is no single location for central units and BBU pools. Each of the larger transport network domains may have their own CU/BBU pool sites. The same also applies to DUs. For instance, a DU may be located in an evolved RRH, in an aggregation node conn