nd NFV enables dynamic, flexible deployment and on-demand scaling of NFs, which are necessary for the development of the 5G packet core network. Such characteristics have also encouraged the development of network slicing and service function chaining. From a UE perspective, slicing a network is to group devices with similar performance requirements (transmission rate, delay, throughput, etc.) into a slice. From net- work perspective, slicing a network is to divide an underlying physical network infrastruc- ture into a set of logically isolated virtual networks. This concept is considered as an important feature of a 5G network, which is standardized by 3GPP. Service function chain- (SFC)25 or network service chaining allows traffic flows to be routed through an ordered Network service chaining or service function chaining is a capability that uses software-defined networking capabilities to create a service chain of connected network services and connect them in a virtual chain. This capability can be used by network operators to set up suites or catalogs of connected services that enable the use of a single network connection for many services, with different characteristics. The primary advantage of network service chaining is the way virtual network connections can be set up to handle traffic flows for connected services. For example, a software-defined networking controller may use a chain of services and apply them to different traffic flows depending on the source, destination, or type of traffic. 38 Chapter 1 Signaling control entity SGW/PGW PDCP-C Central unit PDCP-U Local 5G BTS Local 5G BTS management management Figure 1.15 Centralized PDCP with centralized RRM in separate platforms [34]. list of NFs (e.g., firewall, load balancers, etc.). The best practical use case of SFC is to chain NFs (i.e., middle boxes in this case) placed in the interface between PGW and the external networks. As depicted in Fig. 1.16, the network slicing architecture comprises three layers: (1) service instance layer, (2) netw