Detecting network congestion at a network device by collecting, for various time intervals, measurements of a quantifiable characteristic of traffic transiting the network device at a plurality of respective measurement times during each of the time intervals. Described systems and methods select two or more sets of measurements, each set corresponding to a respective time interval; determine, for each of the selected sets of measurements, respective upper and lower boundaries for the quantifiable characteristic during the respective time interval; and analyze trends for a time window inclusive of the time intervals corresponding to the selected sets of measurements, the trends including an upper boundary trend and a lower boundary trend. Congestion is then identified responsive to the analysis detecting a substantially constant upper boundary trend concurrent with a rising lower boundary trend.