A tamperproof ClientID system to uniquely identify a client machine is invoked upon connection of a client application to a backend. The change order may include specific requested denominations of paper cash andor coins. At least one of the polymer electrolyte membrane, anode catalyst layer, gas diffusion layer at the anode side, cathode catalyst layer and gas diffusion layer at the cathode side includes metallic nanoparticles having an average particle diameter different from that of the core-shell type catalyst particles and including the shell metallic material. In the upstream direction each ONU transmits at most one burst per frame that includes a header and a payload containing a variable number of bytes that is adjustable on a continuum.