[ntp:questions] long linear network, time accuracy, and ntp strata

Miernik, Jerzy (Jerzy) jerzy.miernik at alcatel-lucent.com
Mon Oct 18 21:49:47 UTC 2010

I have a question about how to use ntp in a long linear network. Assume there are 50 nodes with the one most in the West having GPS, and every node running ntpd:
  node1 --- node2 --- node3 --- ... --- node50

Which approach to synchronization would be better in terms of the time accuracy in nodes:
1. configure 'server node1 ...' in nodes 2, 3, ..., 50; or
2. use manycast for automatic client / server self-organization?

Approach 1 seems to me to lead to inferior accuracy due to increasing distance between a client in nodex and server in node1, where routing in nodes node2, node3, ..., node(x-1) would add to jitter. Yet we would have one node stratum1 and all others stratum2, it would seem...

I would think approach 2 with manycast would end up in smaller offsets (if any) between clocks, but would lead to clocks of stratum 16, 17, ..., 50, and I am not sure how ntpd would react in node16, node17, ..., node50. 

Could an expert please offer a comment on which approach would be preferable? 

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