Ethernet Ethernet PHY C&M: Control and management VLAN: Virtual LAN OAM: Operations, administration, and maintenance IPsec: Internet protocol security UDP: User datagram protocol MACsec: Media access control security ICMP: Internet control message protocol SNMP: Simple network management protocol Figure 1.33 eCPRI protocol stack over IP or Ethernet [76]. management plane; and synchronization plane. The control and management information exchanged between the control and management entities are within the eREC and the eRE. This information flow is provided to the higher protocol layers and is not considered to be time critical. An eCPRI protocol layer for the user plane is defined, as shown in Fig. 1.33. The eCPRI specification identifies Ethernet and IP as two transport options for the user plane. It further defines certain messages for the user plane, which include user data, real- time control data, and other services. The I/Q Data and Bit Sequence message types are defined for the user data whose selection depends on the functional split that is used. The Real-Time Control Data message type is defined for real-time control information. These message formats are shown in Fig. 1.34. The eCPRI specification does not provide the detailed description of the information fields of the above message types. In these message formats, the following fields are identified: PC_ID (an identifier of a series of I/Q Data Transfer messages; or an identifier of a series of Bit Sequence Transfer messages), RTC ID (an identifier of a series of Real-Time Control Data messages), SEQ_ID (an identifier of each message in a series of I/Q Data Transfer messages; or an identifier of each message in a series of Bit Sequence Transfer messages), I/Q samples of user data (a sequence of I/Q sample pairs (I,Q) in frequency domain or time domain and associated control information, if necessary), bit sequence of user data, real- time control data, whose interpretation is left to implementation. Therefore, the details of 5G Network Architecture P