Methods and systems are provided for identifying congestion and anomalies at individual nodes, links, and segments in a network. In accordance with an embodiment of the invention, a monitoring station determines for each link in the network a statistical model based on a harmonic analysis. The monitoring station collects from each link metric data. The monitoring station then selects for each link a model that includes one or more harmonic components. By estimating parameters of the harmonic components, the monitoring station then captures the periodicity of the collected metric data in the harmonic components of the model. The monitoring station uses the model to estimate the state of the network from which estimated values of the metric data are determined. The monitoring station then determines whether congestion or anomalies exist in the links based on the estimated metrics.