ngth division multiplexing channel is spaced 20 nm apart from the adjacent channel (www.Smartoptics.com). DWDM channels 0.8 nm spaced apart 1310 region 1550 region CWDM channels (20 nm apart) 10 Chapter 1 control-plane and user-plane functions were separated, and ultimately network slicing and edge computing have been introduced to further advance the network architectures toward flexibly supporting various 5G use cases and applications. Having the above principles and requirements in mind, 3GPP 5G system (5GS) architecture has been designed to support data connectivity and new services by enabling deployments to use SDN/NFV methods. The 5GS architecture leverages service-based interactions between control-plane NFs and supports separation of user-plane functions from control-plane functions. The modularized functional design would allow flexible and efficient network slicing. It defines procedures, that is, set of interactions between NFs, as services SO that their reuse is possible. It enables each NF to directly interact with other NFs. The 5GS design minimizes dependencies between the access and the core networks. It further supports a unified authenti- cation framework, stateless NFs, where compute resources are decoupled from storage resources, and capability exposure, as well as concurrent access to local and centralized ser- vices. The 5GS supports roaming with both home-routed traffic as well as local breakout traffic in the visited network. In 5GS, the interactions between NFs are represented either through a service-based representation, where NFs within the control plane enable other authorized NFs to access their services which may include point-to-point reference points; or a reference-point representation, where the interactions between the NFs are described by point-to-point refer- ence points between any two NFs. The NFs within the 5GC network control plane use service- based interfaces for their interactions [3]. The general principles that guided the definition of 3GPP 5G radio access network (