From: Dave Taht <dave.taht@gmail.com>
To: "Ron Frazier (NTP)" <timekeepingntplist@c3energy.com>
Cc: thumbgps-devel@lists.bufferbloat.net
Subject: Re: [Thumbgps-devel] Project clarification
Date: Tue, 13 Mar 2012 20:08:02 -0700 [thread overview]
Message-ID: <CAA93jw7pqkxUjLku1HySara9Le96Anh9s8X5DFoi8_vUYf_qEQ@mail.gmail.com> (raw)
In-Reply-To: <4F5FF42B.9060900@c3energy.com>
On Tue, Mar 13, 2012 at 6:28 PM, Ron Frazier (NTP)
<timekeepingntplist@c3energy.com> wrote:
> On 3/13/2012 9:10 PM, Dave Taht wrote:
>>
>> On Tue, Mar 13, 2012 at 4:06 PM, Eric S. Raymond<esr@thyrsus.com> wrote:
>>
>>>
>>> Mike Hord<mike.hord@sparkfun.com>:
> I'd like to get a further minor clarification on the project goal. Do you
> want your time reading to be within plus or minus 1 ms of UTC, for a total
> range of 2 ms? Or do you want it to be within plus or minus 500 us of UTC,
> for a total range of 1 ms?
Heh. Good question.
As good as it is possible to get without having to have rubidium
clocks embedded in the stick?
Better than 10ms is desirable, and the 1ms is something of an
arbitrary goal. Nyquist theorem applies, and then there's slop/noise
elsewhere in the system that will start cropping up (interrupt
latency, etc)
Trying to clearly identify problem hops from multiple sides is
dependent on the 'distance' inherent in the underlying technology. If
we wanted to identify problems on a single 10GigE ethernet segment,
that's measured in *ns*. We don't, thankfully.
First hop out of a router is generally 1ms, same for wireless. Cable
is in the 2ms-8ms range. DSL, up to 60ms, same for wimax...
So < 5ms would be the outside goal, and anything less than that - so
long as it can be thoroughly catagorized - is a bonus.
Continental US distances are 60-100ms...
>
> Sincerely,
>
> Ron
>
>
> --
>
> (PS - If you email me and don't get a quick response, don't be concerned.
> I get about 300 emails per day from alternate energy mailing lists and
> such. I don't always see new messages very quickly. If you need a
> reply and have not heard from me in 1 - 2 weeks, send your message again.)
>
> Ron Frazier
> timekeepingdude AT c3energy.com
>
>
> _______________________________________________
> Thumbgps-devel mailing list
> Thumbgps-devel@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/thumbgps-devel
--
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net
next prev parent reply other threads:[~2012-03-14 3:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-13 21:46 Mike Hord
2012-03-13 23:06 ` Eric S. Raymond
2012-03-13 23:30 ` tz
2012-03-14 1:18 ` Eric S. Raymond
2012-03-14 1:10 ` Dave Taht
2012-03-14 1:28 ` Ron Frazier (NTP)
2012-03-14 1:53 ` Eric S. Raymond
2012-03-14 3:08 ` Dave Taht [this message]
2012-03-14 3:42 ` Dave Taht
2012-03-14 4:02 ` Ron Frazier (NTP)
2012-03-14 4:32 ` Eric S. Raymond
2012-03-14 12:44 ` tz
2012-03-14 2:28 ` tz
2012-03-14 2:46 ` Dave Taht
2012-03-14 3:05 ` tz
2012-03-14 4:36 ` Patrick Maupin
2012-03-14 5:00 ` Eric S. Raymond
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