The present disclosure is a decentralized Software Defined Network (dSDN) which runs individual dSDN controllers at each router in the network, disseminating network state via an inter-router communication protocoll. In some examples, the dSDN is an underlay and is coexistant with an out-of-band software defined network (SDN) control plane, thus achieving a unified architecture that applies across both overlay and underlay. In both the overlay and the underlay, path computation is based on global state, such as a complete view of a network connectivity graph and traffic demands. An end-to-end path that a packet takes may be determined by a localized computation that is run at a single node, such as an SDN controller in the overlay or a head-end router in the dSDN underlay. The network may be partitioned into domains and the same approach may be applied within and across domains.