The following guidelines can help you to organize the hierarchy structure for the servers:
Whenever possible, specify Secondary time servers to synchronize with time sources. In this case, the time sources are Primary, Single, or Reference time source.
Keep to a minimal number of time sources to reduce the network traffic. The number of packet exchanges between two servers doubles during each polling interval.
Use time sources to provide local access throughout the network. On a large network, the use of multiple time sources can reduce the overall traffic across routers.
Avoid using Primary time servers across WAN. This will minimize the traffic across WANs for time synchronization that may occur due to voting.
If you are configuring for a multiple network, distribute Primary time servers strategically across the WAN infrastructure. This will reduce the WAN traffic by providing a time source for Secondary time servers and client workstations at each location.
If the WAN infrastructure requires more than seven Primary time servers in the time provider group, implement additional time provider groups as necessary. Ensure that each Reference time server is synchronized to the same time source.
All other servers in the network should be designated as Secondary time servers.
