The above arrangement should provide very good, robust time service with a minimum of traffic to distant servers and with manageable loads on the local servers. While it is theoretically possible to extend the synchronization subnet to even higher strata, this is seldom justified and can make the maintenance of configuration files unmanageable. When justified by the accuracy expectations, NTP can be operated in broadcast and multicast modes, so that clients need only listen for periodic broadcasts and do not need to send anything. While it is a rather simple task to set server clocks accurately, the design, coordination, and deployment of a Federal Network Time Synchronization system is much more complex. This version enhances the robustness of NTP in the face of major network disruptions.
Errors are the author's responsibility.
Other consideration were noted above.