[ntp:questions] Quality vs. Quantity

Terje Mathisen terje.mathisen at tmsw.no
Mon Mar 24 17:42:59 UTC 2014

Paul G wrote:
> (I inadvertently sent this only to Terje Mathisen)
> On Sun, Mar 23, 2014 at 12:07 AM, Danny Mayer wrote:
>> What do you mean by load-balancing? NTP cannot be load-balanced.
> Of course it can (at some cost).

Obviously. As I noted plain ntp client requests, without signatures or
any other stateful features, can indeed be serviced by multiple servers
as long as they are all keeping the exact same (within the network
timing jitter limits) time.

In a national lab I'd assume that those S1 servers are kept at the
sub-us level.
> On Sun, Mar 23, 2014 at 3:43 AM, Terje Mathisen wrote:
>> You really do NOT want load-balancing of ntp servers!!!
> Ideally the server would manage this but address based load balancing
> (presumably as practiced by USNO) solves some problems.  DNS
> balancing (viz. time.nist.gov or pool.ntp.org) is pretty weak but
> some of that can be mitigated in the server.  Still I'd rather have
> three IP addresses fronting 300 servers than three IP addresses
> fronting three servers assuming the goal is resilient remote
> service.

Even better would be 300 IP addresses fronting those 300 servers, with 
some form of round-robin DNS and the use of the pool directive by the 
> But I might still question the assumptions of the OP (the question is
> unclear) since I expect the number of queries to central "public"
> infrastructure to decline over time as the number of clients
> decrease.


I'd rather expect the current trends to continue, with more and more 
gear starting to use (often very bad subsets of) the ntp protocol for 
time sync.

In an idea world we would have lots & lots of S1 and S2 servers all 
around the world, and all the clients would use 'pool' to automatically 
detect the best servers to connect to.


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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