||Software-Defined Networking (SDN) is an emerging network architecture decoupling the network control and forwarding functions, and it enables the network elements to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. SDN is ideal for the bandwidth hungry and dynamic nature of today’s applications, since it permits through a logically centralized controller to reconfigure instantaneously the network, thus exploiting the network capacity more efficiently than distributed routing protocols. Looking at classical networking problems through the angle of centralization brings very challenging and new online network optimization problems. These problems were not considered when everything was done at network planning phase with no hard time constraints. This talk gives an introduction to this new domain and presents a few contributions on fast connection setup and network re-optimization.