In a network diagnostics system, network topology discovery determines the links that make up the network, artificial call quality management determines the set of test calls that need to be made to test the network, and real call quality management collects call-quality data about real calls in the network. The set of test calls is reduced by calls that would duplicate paths, or portions of paths, of the real calls, and artificial call quality management performs only the test calls of the reduced set and collects call-quality data thereon. Analysis analyzes the combined data of the real calls and the test calls to determine the possibly-bad call paths in the network.