[ntp:questions] Hardware SNTP server

Brad Knowles brad at stop.mail-abuse.org
Thu Sep 8 12:30:22 UTC 2005


At 11:14 AM +0900 2005-09-08, Hiroshi Toriyama wrote:

>  Can anyone point out whether such server is suitable
>  for a public stratum 1 server?

	If you're the only ones using it, I guess you can do pretty much 
whatever you want.


	However, speaking only for myself, if you wanted to get it 
included in pool.ntp.org, or on the public lists of NTP time servers 
underneath the page at <http://ntp.isc.org/bin/view/Servers/WebHome>, 
then I'd want to see you running a full NTP implementation, 
preferably NTPv4.  I would not want to see any SNTP server listed in 
any of those places.

	Indeed, I wouldn't want to see any public Stratum-1 server 
running only SNTP, instead of at least NTPv3, if not NTPv4.

	I have no problem with people running SNTP clients, if their 
application is such that they can't support running a full internal 
NTP server as a "client".  But IMO it is not appropriate to run a 
public SNTP server that you encourage others to use.


	I'm sorry, I know that this sounds really down, and I'm not 
recognizing the amazing work you've done with putting a complete SNTP 
server into FPGAs.  FPGAs are hard to program, run amazingly fast 
(relative to general-purpose CPUs), and have a number of interesting 
uses.

	However, I've recently heard about at least two different large 
groups of people (all from Japan, strangely enough), that are 
implementing all sorts of stuff in FPGAs that they think will be a 
huge improvement for the world, but they turn out to only be solving 
the easy 1% of the problem, and not understanding that the part of 
the problem they're solving is not generally an issue.


	In the case of one group I've talked to recently, they're talking 
about building L3-L7 special-purpose anti-spam switches using FPGAs, 
but product-wise they're only offering two particular features which 
are not typically serious performance issues in existing software 
only solutions, and they don't appear to offer anything that isn't 
already available from a dozen (or more) existing companies in the 
field, many of which are already using even higher-speed ASICs in 
their devices.  Moreover, they don't seem to be likely to be able to 
offer their features at a world-beating price that would otherwise 
give them a competitive advantage.

	They seem to be coming to this party much more than a day late, 
and much more than a dollar short.  And yet, their engineers still 
seem to think that sprinkling some magic FPGA dust is going to solve 
all their problems.  I wish them luck, but unless they radically 
change their services model and attack problems which do currently 
pose serious CPU performance issues in this field and which are not 
addressed by any existing or known-to-be-coming ASICs, I don't see 
how they can possibly succeed.


	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.



	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.

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.



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