Traffic demand is increasing dramatically, year on year, with typical growth figures of up to 60% for Internet based traffic. Such traffic increase is impacting on both network costs and power consumption. Moreover, traffic is not only increasing but becoming much more dynamic, both in time and direction. For these reasons, transport network evolution from current DWDM systems towards elastic optical networks, based on flexgrid transmission and switching technologies, could significantly increase both transport network scalability and flexibility. Further benefits come from multilayer interworking mechanisms enabling electronic switching technologies (IP/MPLS, OTN, etc) to directly control the bandwidth of the Bandwidth Variable Transponders (BVT) for optical bandwidth optimization purposes.This then defines the key objective behind IDEALIST: To research in detail a cost and power efficient transport network architecture able to carry a wide range of signal bandwidths, each of which will be varying in real time in direction and magnitude, and some of which will be extremely large and possibly exceeding 1Tb/s. The network architecture proposed by IDEALIST is based on four technical pillars:• Transport systems enabling flexible transmission and switching beyond 400Gbps per channel.• Control plane architecture for multilayer and multidomain elastic optical networks.• Dynamic network resources allocation at both IP and elastic optical layers• Multilayer network optimization tools enabling both off-line planning and on-line network re-optimization in elastic optical networks.The intention is that the IDEALIST network architecture will be easily industrialised. Therefore, feasibility studies and experimental implementation and demonstration of prototypes will be key activities, as well. IDEALIST will also feed the collaboration with other Projects and the submission of contributions to ITU-T, OIF, IETF, thus reinforcing European position in standardization bodies.