236 ITU‐T's Technical Reports and Specifications Figure 20 – Communication layer 2.1.2.1 Transport networks The convergence of infrastructure already introduced earlier should be considered carefully for this type of transport of data networks in urban environments. To transport the large amount of data that handled the smart sustainable cities will be necessary for local governments to implement national policies for the deployment broadband networks. Optical Transport Fiber is the optimum physical medium to transmit large amounts of data over long distances. The bandwidth‐over‐distance capabilities of fiber by far exceed those of any other medium such as copper or wireless technologies. Fiber‐optic transport is therefore the unchallenged foundation for all high‐speed networks. Figure 21 – Fiber optic networks worldwide