[ntp:questions] Re: Hardware SNTP server

Hiroshi Toriyama tori-sec at nict.go.jp
Tue Sep 13 10:29:57 UTC 2005


Brad Knowles wrote:

 > In your case, you're implementing an SNTP Stratum-1 server,
 > but even if you put all the people in your country on VOIP or
 > 4G mobile phones and needed highly accurate time services to
 > all these devices, I think you'd still be hard-pressed to show
 > a real client-impacting performance difference between your FPGA
 > SNTP server and a real NTPv4 server based on the Poul-Henning
 > Kamp Soekris+FreeBSD+Oncore SBC solution.
 >
 > IMO, the latter would be much cheaper to buy, configure, and
 > operate, and provide better overall quality time (as a result
 > of improved internal algorithms).  Although the jitter for
 > the PHK-style solution might be a bit higher than 8 nanoseconds,
 > and they might not be able to handle as many clients per server,
 > you could compensate for that by using more of them in a
 > good-quality distributed hierarchy. Moreover, by having more of
 > them, you'd be able to locate them closer to the clients, and
 > that improved geographical locality could easily overwhelm an
 > eight nanosecond jitter.

Yes, precision of 8ns will not be advantage for internet use,
I know even one L2 switch may add 20 to 500 ns jitter.

I think that the main advantage of our server is in the low degree
of operation cost, not the equipment cost itself.

 >     At the very least, I'd want to hear more about your proposed usage
 > model, which you believe would prohibit the use of standard NTPv4
 > servers running well-configured hardware and OS, and would instead
 > require the use of your custom FPGA SNTP servers.

I've designed the hardware SNTP server mainly for national time
standard organizations.
It will be, so to speak, the internet version of JJY or DCF-77.

I beliebe it also suits major internet providers or major time
service providers who have atomic clocks adjusted to national
standard.

I think that distributed ntp network is not always
cost-effective for such purposes.
Thogh geographical locality is still important, I feel its
importance is decreasing by speeding up of the network.
For example, some DNS round-robin disregards the geographical
locality, but typical PC users don't mind it.

Concentrated server can be built with many ntpd servers and
a L4-L7 load balancer, but but a hardware SNTP server must be
implemented simpler than the load balancer.
This is the basic idea of our SNTP server.

Hiroshi Toriyama
Time Applications Group
NICT, Japan




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