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Re: [gpsd-dev] Clarifications needed for the time-service HOWTO
From: |
Beat Bolli |
Subject: |
Re: [gpsd-dev] Clarifications needed for the time-service HOWTO |
Date: |
Wed, 23 Oct 2013 20:48:02 +0200 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 |
On 22.10.13 04:10, Gary E. Miller wrote:
> The jitter from NMEA on a local GPS can be a few hundred mSec. Run a
> traceroute to a server and you see how bad you network can be. Cable
> modems could be up to 500 mSec (and they are wildly asymetric). The
> jitter from a local GPS s defined by the USB transfer, around 1 mSec
> for USB 1.1 The jitter from interrupt processing can be 100uSec and
> sometimes much worse on a loaded system.
I just wanted to note that I took the ntpq -p output that got merged
into the tuning HOWTO right at the moment when I wrote the patch and was
not edited in any way. I have a consumer cable setup with 30Mbps upload
and 3 Mbps download, so quite asymmetric.
The servers with the worst jitter are:
mimir.fcom.ch - my ISP's. Strange because it's just three hops away.
Maybe hosts other services and is under a lot of load.
ntp.univ-angers.fr - in a different country and 15 hops away, so
probably network related.
ntp.ethz.ch - the NTP server of ETH Zurich, one of the two federal
research institutes in Switzerland. Probably half of Switzerland is
synchronizing with this server :-)
Beat
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- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, (continued)
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/21
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Hal Murray, 2013/10/22
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Dave Platt, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/24
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Hal Murray, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO,
Beat Bolli <=
Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Miroslav Lichvar, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Hal Murray, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/23
- Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Hal Murray, 2013/10/23
Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Hal Murray, 2013/10/23
Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Eric S. Raymond, 2013/10/24
Re: [gpsd-dev] Clarifications needed for the time-service HOWTO, Gary E. Miller, 2013/10/24