Like highways, communications networks can get snarled up when they have too much traffic. Most people have experienced this in the form of the "Mother's Day effect." A more serious form of this limitation occurs when an emergency results in a sudden surge of calls to a local 9-1-1 call center, resulting in congestion and call blocking. Next generation 9-1-1 (NG911) uses IP-based technology to manage 9-1-1 call surges dynamically, minimizing blockage.
For more on NG 911 watch the video below: