ubclass applies to functional split options 2 and 3 with longer transport distances, and the very high-latency subclass is applicable to functional split option 1 or legacy trans- port that connects the access and core networks with much longer transport distance. Network slicing enables next-generation network to provide multiple type of services and applications with different service requirements under a common and shared physical net- work infrastructure. An NGFI-compliant transport network supports transport of the network slicing traffic and serves as a sub-network instance and resource manageable by the network slicing orchestrator. From architectural perspective, two operation modes may be defined depending on the level of transparency to the network slicing. In slicing-agnostic transport mode, the NGFI deployment scenarios may coexist across multiple instances in the same transport network segment, potentially owing to variations in RAN node (RRU, DU, CU) locations that resulted from network slicing operation. 86 Chapter 1 Therefore, it is possible that multiple classes of service be simultaneously enacted in a transport connection between two network nodes. The combined classes of service are logically presented in Fig. 1.38, which are supported by a slicing-agnostic transport net- work. The slicing-agnostic transport is able to provide multiple levels of transport ser- vice and to maintain different transport QoS based on the class of service requirement. It also performs transport key performance indicator (KPI) monitoring and reports the results to NGFI operation and maintenance (OAM), on the basis of classes of service. The transport network in this mode is not directly aware of the network slicing opera- tion. Instead, it simply makes the classes of service available via its interface to the other network entities, where a slicing-to-classes of service mapping needs to be per- formed by aggregating the slicing traffic with similar KPI requirements. If RAN nodes that support the sliced services are 