Network devices that (a) test that GPS-clock enabled network devices have synchronized clocks, (b) identify non-GPS-clock enabled network devices with symmetric latencies as likely to be synchronized to GPS-clock enabled neighbor devices, (c) determine clock skews of remaining network devices not identified in (a) or (b) against the network devices identified in (a) and (b), and re-evaluate latencies of the GPS-clock enabled network devices, the non-GPS-clock enabled network devices, and the remaining devices based on the results of (a)-(c).