A method and apparatus for measuring pattern shifts in call patterns, e.g., call volumes and/or feature usage in a packet network, e.g., a VoIP network is disclosed. The present method collects performance data over a set period of time and constantly compares each periodic sample with the previous periodic sample on a rolling window basis. Changes of a pre-defined percentage threshold, e.g., approximately 30%, or more in a current sampled period are alarmed and monitored to preclude potential service disruptions. In one embodiment, upon receipt of these alarms, network elements that are vulnerable to discontinuities due to overload can be automatically reset or cleared of hung processes.