9]. Introduction of physics in the communication model allows us to walk on the boundaries of the communication data rate avoiding the risk of obtaining non- physical solutions. References E. Basar, M. Di Renzo, J. De Rosny, M. Debbah, M.-S. Alouini, R. Zhang, Wireless communications through reconfigurable intelligent surfaces. IEEE Access 7, 116753-116773 (2019) 2. S. Dang, O. Amin, B. Shihada, M.-S. Alouini, What should 6G be? Nat. Electron. 3(1), 20-29 (2020) 3. E. Björnson, Ö. Özdogan, E.G. Larsson, Reconfigurable intelligent surfaces: three myths and two critical questions. IEEE Commun. Mag. 58(12), 90-96 (2020) 4. E. Basar, Reconfigurable intelligent surface-based index modulation: a new beyond mimo paradigm for 6G. IEEE Trans. Commun. 68(5), 3187-3196 (2020) 5. M. Di Renzo, A. Zappone, M. Debbah, M.-S. Alouini, C. Yuen, J. De Rosny, S. Tretyakov, Smart radio environments empowered by reconfigurable intelligent surfaces: how it works, state of research, and the road ahead. IEEE J. Select. Areas Commun. 38(11), 2450-2525 (2020) 6. A. Pizzo, T.L. Marzetta, L. Sanguinetti, Spatial characterization of holographic mimo channels (2019). Preprint. arXiv:1911.04853 We recall that fixed an e-net of A is a subset A' of a metric space A such that A' is finite and Ax E A, 3yeA':d(y, < E, wherein d(.,- is the distance. A totally bounded set in a metric space contains a e-net AE > 0. 2 Information Flows at the DPL Level 7. A. Pizzo, T.L. Marzetta, L. Sanguinetti, Degrees of freedom of holographic mimo channels (2019). Preprint. arXiv: 1911.07516 8. A. Pizzo, T.L. Marzetta, L. Sanguinetti, Spatially-stationary model for holographic mimo small-scale fading. IEEE J. Select. Areas Commun. 38(9), 1964-1979 (2020) 9. M.D. Migliore, Horse (electromagnetics) is more important than horseman (information) for wireless transmission. IEEE Trans. Antennas Propag. 67(4), 2046-2055 (2018) 10. L. Brillouin, Science and Information Theory (Academic Press, New York, 1959) 11. D.S. Lebedev, L.B. Levitin, Information transmission by electro