Performance data relating to each of multiple network devices distributed in a geographic region is analyzed. That data can include values for various parameters measured automatically by routine polling of subscriber devices and/or network elements serving those subscriber devices. Measured parameter values can then be stored in a database and made available, together with information about subscriber device locations, to one or more analysis servers that analyze different portions of the network. As part of that analysis, groups of devices experiencing performance problems are identified based on device location. Information about those groups is then communicated and can be made available for, e.g., monitoring by service personnel.