scalability of user plane and control plane; and centralizing RRM with local breakout of data connec- tions of some UEs closer to the base station site. During the establishment of an Sx session, the control plane function and the user-plane function select and communicate to each other the IP destination address at which they expect to receive subsequent request messages related to that Sx session. The control-plane function and the user-plane function may change this IP address subsequently during an Sx session modification procedure. Typically, Ethernet should be used as a layer-2 protocol, but the network operators may use any other technologies. Domain name system is a hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates more readily memorized domain names to the numerical Internet protocol addresses needed for locating and identifying computer hosts and devices with the underlying network protocols. The domain name system delegates the responsibil- ity of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over subdomains of their allo- cated name space to other name servers. This mechanism provides distributed and fault-tolerant service and was designed to avoid a single large central database. The domain name system also specifies the technical functionality of the database service that is at its core. It defines the domain name system protocol, a detailed specification of the data structures and data communication exchanges used in the domain name system, as part of the Internet protocol suite. 5G Network Architecture SGW/PGW Central unit PDCP-U Local 5G BTS management PDCP-C Figure 1.14 Centralized PDCP-U with local RRM [34]. 1.1.4 Network Slicing The combination of SDN a