As society moves toward digitization, the network supporting a digital society must likewise evolve. NTT has taken up the research and development (R&D) of a network infrastructure called Cognitive Foundation ® in order to solve a wide variety of problems in our digital society. This article introduces specific R&D achievements based on the following R&D directions of network technology for the future digital society: (1) R&D of competitive network infrastructure technologies, (2) advanced and smart network operation supporting digital transformation of the NTT Group, and (3) global environmental protection and optimal use of energy.