A method, information processing system, and computer program storage product for determining if an application has become unresponsive. Network traffic at a receiver node is monitored. The receiver node is determined to have generated a window probe response indicating a predetermined window size. A threshold associated with the window size of the receiver node is set in response to the receiver node having generated the window probe response. The window size of the receiver is determined to have been at the predetermined size for at least one of a time period greater than the threshold and a count greater than the threshold. An application associated with the receiver node is classified as unresponsive in response to the window size of the receiver node having been the predetermined size for at least one of a timer period greater than the threshold and a count greater than the threshold.