arket. A generalized data center architecture for a CU/DU system is shown below in Fig. 4-2: We'll describe individual components here: Fronthaul/Top of Rack (TOR) switch. Provides the fronthaul eCPRI/Ethernet connectivity between the RUs and DUs together with 1588 timestamping and eCPRI (de) )compression. This functionality is implemented in high-end FPGAs or switch-like ASICs with Terabit per second (Tbps) performance classes. 1 Connectivity to the DU blades is provided over Ethernet links carrying uncompressed eCPRI IQ samples for low intensity CPU processing in the DU processor. Chapter 4 Hardware architecture choices Data Center 1..10GbE (to 10/25/40/ distributed DUs) ToR Switch Or 10..25 GbE (to 50/100 Gbps distributed RUs) Gbps to core CU/DU Blades: 1-2x 100GbE Fail-over DU Blade(s) CU Blade(s) PPS/10MHz Timing Control, Power, OAM Storage Edge Compute FIGURE 4-2 Data center architecture. Timing is provided by a separate time server solution that is optimized for performance and provided by a specialized solutions vendor. The time server acts as a timing source towards many RUs at once through the TOR switch as well as providing a Pulse Per Second (PPS) and/or frequency accurate source towards the DU blades. CU blades perform CU processing, including (optional) support for IP Security (IPSec) for backhaul security. Key interfaces are shown in the figure below (Fig. 4-3), with an integrated (traditional macro base station) option shown on the left side and the disaggregated solution on the right side. The 5G New Radio (NR) gNB (Base Station) is connected to Access and Mobility Management Function and User Plane Function in the 5G Core Network (5GC). Key interfaces, all defined by 3GPP and shown below in Fig. 4-4, include: NG-C: Control Plane (CP) interface between NG-RAN and 5GC NG-U: User Plane (UP) interface between NG-RAN and 5GC El: CP/UP interface within the (logical) PDCP component and provides transport of signaling between Control Plane and User Plane F1-C: CP interface between CU and DU F1-U: UP int