156 ITU‐T's Technical Reports and Specifications Figure 3 – Multi‐tier SSC ICT meta‐architecture13 A smart sustainable city can also be considered a system of subsystems. With regard to its technical definition, it can be viewed from different perspectives. Figures 4 and 5 demonstrate the communications view of the SSC ICT architecture, based on a physical and an information flow perspective respectively. Both perspectives of this view are multi‐tier. ____________________ 13 Technical Specification on “Setting the framework for an ICT architecture of a smart sustainable city” (fg‐ssc‐0345)