Unruh and Terje, thank you for replying. What if we complicated networking somewhat, such that at times node50 acquires GPS capability while node1 may looses it? Actually, to make the problem general, any one node (possibly only one) may have GPS and remain at an extremity of the network, where indeed the traffic between 'outer' nodes must be routed through all other 48 nodes forming a chain of 49 hops. So, sometimes node2 may have GPS too, like this:
Node2 --- node3 --- node1 --- node4 --- .... --- node49 --- node50 GPS Or nodes node1, node2, node3, node4 have GPS in some kind of a 'normal' network of four, with a long tail (like in a kite) of 46 nodes attached to one of the four. How best could we write ntp.conf, to synchronize time in such special networks? Warm regards, Jerzy. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of unruh Sent: Tuesday, October 19, 2010 7:37 AM To: [email protected] Subject: Re: [ntp:questions] long linear network, time accuracy, and ntp strata On 2010-10-18, Miernik, Jerzy (Jerzy) <[email protected]> wrote: > 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 > GPS What does "long linear network" mean? Does it really mean that all network traffic between node 1 and node 50 must pass through eachof the other machines ( eg because all have two network cards and the only connection from node i to i-1 is via one card and from i to i+1 is via the other network card on machine i?) If so, you will have a horribly slow network no matter what you do. Almost always direct connection is more accurate-- the outbound and inbound network times are measured for each packet. Not assumed. But as said by others, you want each of those nodes requesting time directly from node 1. ( also note that a chain of 50 machines each asking time from the previous one exhauses the possible stratum numbers and it will not work. ) > > 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? > Sincerely, > Jerzy. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
