[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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