Dedicated network time servers are on the whole reliable pieces of hardware and very rarely do they fail to receive and distribute a timing signal. However, some common errors do occur:
Network time servers that receive a time signal from the GPS satellite system can often fail to find a signal if they have not been given enough time to lock on to a satellite. All GPS network time servers should be left on for at least 48 hours to ensure the time server can get a stable lock on a the satellites.
Network time servers that receive a radio signal can also fail, the most common reason is that the signal is being blocked by interference. Move the time server away from any other electrical equipment; even just tilting the network time server can increase the signal strength as the antenna should be perpendicular to the signal.
Radio signals are also disrupted for scheduled maintenance users of the UK’s MSF signal should check with the National Physical Laboratory for planned outages.
Network time servers are also vulnerable to over subscription if a network consists of a lot of machines all trying to receive a time signal then the bandwidth can be taken up with time requests. Ensure the correct use of stratum to alleviate the problem.