A system and method for network planning with certain guarantees is disclosed. The system receives data characterizing various aspects of a backbone network, such as the nodes of the backbone network, how the nodes are connected by network links, the maximum available capacities of the network assets, network costs, and network asset reliability information. The system also receives data characterizing the requirements of different data communications, or flows, within the backbone network. For example, the backbone network may need to provide a flow a minimum amount of bandwidth or throughput, and the flow may have a minimum required uptime or availability. Based on the network data and flow data, the system generates a network plan that describes how capacity should be provided by different components of the network in a manner that guarantees satisfying flow requirements while balancing other considerations, such as network costs.