Tech Solvency: NTP

This is my NTP lab - stats for my NTP servers, and other NTP resources and notes.

Tech Solvency NTP servers

The NTP lab is used to monitor Alaskan NTP servers, and for general NTP exploration and reference.

interval-alix2d13 (ALIX 2d13 Slackware + Navisys GR-701W (USB) + NTPsec)
tackleberry-uputronics (Raspberry Pi 3 B+ Raspbian + Uputronics HAT (u-blox MAX-M8Q) + NTPsec)
Graph overview

Other NTP server graphs - ntpviz-based

pi3.rellim.com - Pi (Gentoo 64-bit) + Uputronics HAT + NTPsec
pi4.rellim.com - Pi (Gentoo 64-bit) + Adafruit HAT + NTPsec
GEM Supermicro + MR-350P
time.arihanc.com - Pi + Adafruit HAT + NTPsec
ntpsec.anastrophe.com
flyingplatypus.org
www.nthead.co.uk
darethehair.net
keff.org

Other NTP server graphs - non-ntpviz

jikan.ae7.st - public stratum 2 (@atoponce)
LeoNTP Stratum 1s - commercial appliance (US$300)

Howtos and builds

Stratum 1 Microserver HOWTO (ntpsec)
GPSD Time Service HOWTO (GEM, ESR)
ava.upuaut.net - Pi + Uputronics
coderich.net - Pi + HATs
dl8rds.de - Pi + Trimble Resolution SMT (and many others at dl8rds.de
Quick start NTP on the Raspberry Pi (satsignal.eu) - Pi + HAB (now Uputronics). See also his previous in-depth setup
nguvu.org - Odroid C2 + Uputronics
yeah.nah.nz - Pi 3 + Uputronics
frillip.com - Pi + Adafruit
mythopoeic.org - BeagleBone Green + Adafruit + Chronodot TCXO RTC (DS3231)
framkant.org - Pi (FreeBSD) + Adafruit
xmission.com - Pi + Adafruit (@atoponce; see ae7.st above)
morcant.com - Pi + Adafruit
reeve.com - Pi + Globaltop / Pi + Hab (u-blox MAX-M8Q); GNSS - very detailed and precise; and by an Alaskan
brandon.penglase.net - Pi (Gentoo) + NavSpark + Maxim DS3231
wraith.sf.ca.us - very detailed, historic interest (from before 1PPS was in kernels, etc.) Linux, FreeBSD
ntpi.openchaos.org Pi with non-HAT u-blox module - http://ntpi.openchaos.org/
jackenhack.com - Pi 3 + u-bloxk Neo-7 + Trimble GPSDO + mods
ryandoyle.net - Garmin GPS 18 LVC + FreeBSD
OpenWRT + USB GPS
developers.redhat.com - Pi + Adafruit
hackaday.io - Pi Zero + Venus838LPx-T GPS timing receiver breakout board
gigofham.com - ODROID-C1+ + Adafruit + Armbian
kenyonralph.com Garmin GPS 18x LVC + Linux or FreeBSD
rdlazaro.info - Pi + Adafruit
konspyre.org - Pi + Adafruit
dan.drown.org - Beaglebone Black + Adafruit + chrony
jfcarter.net - interesting "non-build" (what isn't working); GlobalSat ND-105C + chrony + gpsd experimentation
carrierdetect.blogspot.com - Garmin GPS 18x LVC, Ubuntu 12.04 LTS
rjsystems.nl - Garmin GPS 18 LVC
μWWVB: A Tiny WWVB Station

Hardware-specific info

ublox forums post on ublox MAX-M8Q RTC (tl;dr - for internal use only; can't be used as a general RTC)
Uputronics: Pi+ GPS Expansion Board | pinout (pinout.xyz) | US supplier (Airspy.us) | u-blox MAX-M8Q (TCXO) GPS module
DS3231 RTC: datasheet (PDF) | Adafruit breakout | (uses ds1307 kernel module on Raspbian)

Enhanced WWVB (w/phase modulation)

Format
La Crosse Technology - makes an analog wall clock (404-1235UA-SS) that parses it - teardown from leapsecond.com
The Meinberg PZF 600 (receiver for the LANTIME M300) is the closest that might have supported FM phase modulation for enhanced WWVB, but does not (as of 2018-05) :(

VMs

Time Synchronization in Virtual Machines (Meinberg)
Known OS Issues - Virtualization (ntp.org)
Avoiding Clock Drift on VMs (RedHat)
Timekeeping in VMware Virtual Machines (vmware - 2008, so a bit outdated, but good concepts)
Timekeeping best practices for Linux guests (vmware - 2015; NTP in guests recommended, with tweaks)
Timekeeping within ESXi (vmware - 2018 - good blog with concepts and lab tests)
KVM Guest Timing Management (vmware)
lists.ntp.org KVM thread (2014)
notes on NTP in KVM (Paul Gear)

NTS (Network Time Security)

NTS - Network Time Security
Secure Time (Cloudflare)

Other NTP references and resources

Real Life NTP - excellent overview by Aaron Toponce
Dan Drown's blog - technical dives, builds, analysis
leapsecond.com - true time-nuttery: device teardowns, hydrogen masers, etc. - highly detailed
time-nuts mailing list
Chip Overclock time-related posts (includes atomic (CSAC), GPS, WWVB, and Navisys work)
Bill Hammack on how atomic clocks work - very clear and precise treatment. ~4m30.
Swedish Distributed Time Service (ntp.se) - custom FPGAs, 10Gb/s
www.ijs.si/time/ - in-depth analysis and introduction
Alaska NTP latency from L48: ACS
NMEA reference (gpsinformation.org)
Leap seconds (NIST)
NTP Pool Project forum
Article about the NTPsec fork
gpsheartbeat.c - PPS hearbeat status on ALIX 1C status LEDs
Combining NTP with PTP - (Red Hat blog)
anderswallin.net - advanced commentary
ntpspeak - NTP-related vocab
Building Scalable NTP Server Infrastructures (Brad Knowles for ;login, 2008)
The GPS Week Number Rollover Problem
NTP peerstats word secret decoder ring
snippet of Mills on the potential precision of the long time format
brief intro to dynamic calibration
https://www.qcode.co.uk/post/117 - nice NTP PCI writeup

TODO: 1PPS, RTCs, Allen Deviation, WWVB and devices, software (ntp, openntpd, ntpsec, chrony, etc.)

Tech Solvency / NTP