re for sub-6-GHz frequencies, A2 and B2 for mmWave, and A3 and B3 for future high bands over 60 GHz. Sub-6G-Hz assumed a three-sector configuration, while mmWave and higher bands assumed two sectors. Standard Ethernet interfaces of 10G, 25G, 40G, and 100G are utilized. On the client side, 25G is currently the highest single-lane rate supported. 40G and 100G are based on multiples of 10G and 25G, for example, 4 X 10G and 4x25G. Copper interfaces are limited to site internal cabling. Multimedia fiber can reach 100-300 m and has been commonly used in data centers. Single-mode fiber extends to 10 or 40 km and can be used to directly connect to the peer element. Otherwise the client ports interface a transmission device (e.g. WDM) or some other networking device (a switch, router) for connectivity to remote sites. Eth Port Capacity VS. requirement (Sector peak) Eth Port Capacity VS. requirement (User Peak rate) 100G Port 40G Port 25G Port 10G Port 10G Port 10G Port 4,6 4,7 2,3 2,4 Case A1 Case A2 Case A3 Case B1 Case B2 Case B3 Figure 9.7 Ethernet port speeds and 5G requirements. 9 Transport 9.3.2 Networking Technologies Overview An overview of some key networking technologies and protocols is included in Table 9.1, as candidate building blocks for the 5G networking service. Optical technology has introduced a new layer, Layer-0 (Photonic Layer), that has the highest capacities available as physical media, is agnostic to higher layer proto- cols, supports photonic layer multiplexing and switching with high amount of channels, and optionally supports the OTN (Optical Transport Network) hierarchy. Wavelength multiplexing increases fiber utilization and can provide an optical path through a long distance, with OAM and protection capabilities where needed. CWDM (Course Wave- length Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) grids are standardized by ITU-T. In Passive Optical Networks (PONs), currently 10G is the highest bit rate supported for symmetrical PON (like Next Generation NG-PON2, XGS