Abstract: Passive monitoring by network devices can be used to validate a network traffic matrix, which aggregates end-to-end traffic demands between source-destination pairs in the network. Using information regarding the physical and logical topology of the network during the same time period as the traffic matrix, a model of the network is generated. Traffic load on each link between network devices in the network is predicted using the model and the traffic matrix. Actual traffic loads on each link are determined from the passive monitoring data from each network device. By comparing the predicted load with the actual load on each link, a measure of the validity or accuracy of the traffic matrix is obtained. The disclosed techniques can also be applied to validate a network loss matrix.