[Git][NTPsec/ntpsec][master] 9 commits: Expand definition of GPS to document other GNSS
Eric S. Raymond
gitlab at mg.gitlab.com
Sat Dec 24 15:41:17 UTC 2016
Eric S. Raymond pushed to branch master at NTPsec / ntpsec
Commits:
6d39b3ec by Sanjeev Gupta at 2016-12-24T19:52:02+08:00
Expand definition of GPS to document other GNSS
and let us test UTF-8 !!!
- - - - -
3e6dca1c by Sanjeev Gupta at 2016-12-24T20:02:19+08:00
Expanding documentation, GPSDO holdover and IERS
- - - - -
42a1a0d2 by Sanjeev Gupta at 2016-12-24T20:17:45+08:00
More rewriting and expansion of ntpspeak.txt
- - - - -
dac2795f by Sanjeev Gupta at 2016-12-24T20:33:47+08:00
More minor clarifications to ntpspeak
- - - - -
a062b4fc by Sanjeev Gupta at 2016-12-24T21:28:23+08:00
Update location of leapsecond file
and clarify that the eighteen-month insertion is not cannonical
- - - - -
91741b6c by Sanjeev Gupta at 2016-12-24T21:52:05+08:00
Clean up documentation, bit-rot
- - - - -
e2e164bb by Sanjeev Gupta at 2016-12-24T21:53:15+08:00
Add real documentation of timecode
- - - - -
af5851a5 by Sanjeev Gupta at 2016-12-24T21:54:26+08:00
Convert links to https, and fix one
- - - - -
d98cd888 by Sanjeev Gupta at 2016-12-24T21:56:15+08:00
Merge branch 'master' of https://gitlab.com/NTPsec/ntpsec into DOCS
- - - - -
3 changed files:
- docs/leap.txt
- docs/ntpspeak.txt
- docs/tf582_4.txt
Changes:
=====================================
docs/leap.txt
=====================================
--- a/docs/leap.txt
+++ b/docs/leap.txt
@@ -1,11 +1,12 @@
= Leap Second Processing =
-About every eighteen months the International Earth Rotation Service
-(IERS) issues a bulletin announcing the insertion of a leap second in
-the Universal Coordinated Time (UTC) timescale. Ordinarily, this happens
-at the end of the last day of June or December; but, in principle, it
-could happen at the end of any month. While these bulletins are
-available on the Internet at http://www.iers.org[www.iers.org], advance
+Every six months the International Earth Rotation Service
+(IERS) issues a bulletin announcing if there will be a leap second in
+the Universal Coordinated Time (UTC) timescale. Historically,
+only insertions have occurred, about every eighteen months. The changes
+have been at the end of the last day of June or December; but, in principle,
+it could happen at the end of any month. While these bulletins are
+available on the Internet at https://www.iers.org[www.iers.org], advance
notice of leap seconds is also available in signals broadcast from
national time and frequency stations, in GPS signals and in telephone
modem services. Many, but not all, reference clocks recognize these
@@ -31,7 +32,8 @@ of the current month.
When no means are available to determine the leap bits from a reference
clock or downstratum server, a leapseconds file can be downloaded from
-time.nist.gov and installed using the
+the https://www.ietf.org/timezones/data/leap-seconds.list[IETF]
+and installed using the
link:miscopt.html#leapfile[leapfile] command. The file includes a list
of historic leap seconds and the NTP time of insertion. It is parsed by
the +ntpd+ daemon at startup and the latest leap time saved for future
@@ -55,8 +57,8 @@ crude hack by setting the clock back one second using the Unix
Note however that in any case setting the time backwards by one second
does not actually set the system clock backwards, but effectively stalls
the clock for one second. These points are expanded in the white paper
-{millshome}leap.html[The NTP Timescale and Leap
-Seconds]. If the leap timer is less than one day, the leap bits are set
+{millshome}leap.html[The NTP Timescale and Leap Seconds].
+If the leap timer is less than one day, the leap bits are set
for dependent servers and clients.
As an additional feature when the NIST leap seconds file is installed,
=====================================
docs/ntpspeak.txt
=====================================
--- a/docs/ntpspeak.txt
+++ b/docs/ntpspeak.txt
@@ -75,15 +75,20 @@
are derived from spherical trigonometry using the precisely known
positions of satellites in a geocentric coordinate system. GPS
also provides time service; those that emit <<PPS>> are suitable
- as clock sources for Stratum 1 timeservers.
+ as clock sources for Stratum 1 timeservers. In timekeeping, the
+ term is used to refer not only to the US original GPS system,
+ but newer constellations that work on the same principles, such
+ as ГЛОНАСС (the Russian GLONASS), 北斗 (the Chinese BeiDou-2),
+ and the EU's Galileo.
[[GPSDO]] GPSDO::
GPS Disciplined Oscillator. A good crystal is synchronized to
time from a GPS receiver. The combination gets the short term
stability of the crystal and the long term stability of GPS.
With appropriate firmware, the crystal can be used when the
- GPS receiver stops working. Most cell towers have GPSDOs.
- You can usually spot the conical GPS antenna.
+ GPS receiver is temporarily non-operational; see <<holdover>>.
+ Most cell towers have GPSDOs. You can usually spot the conical
+ GPS antenna.
[[GPSD]] GPSD::
The http://www.catb.org/gpsd/[GPS Daemon], an open-source device
@@ -104,7 +109,7 @@
serial link is called "in-band time" to contrast it with the
out-of-band <<PPS>> signal. Abbreviated IBT. Seldom useful
by itself as it tends to have a large random wander from top
- of second.
+ of second. It is however, useful as a count of seconds.
[[leap second]] leap second::
Because the earth's rotation varies in irregular ways (gradually
@@ -112,8 +117,8 @@
absolute terms rather than as a fraction of day length, keeping
time of day synchronized with mean solar time requires occasional,
unpredictable insertions of a standard second in the calendar. Leap
- second notifications are issued by IERS
- (http://www.iers.org/IERS/EN/Home/home_node.html[International
+ second notifications are issued as Bulletin C by the
+ http://www.iers.org/IERS/EN/Home/home_node.html[International
Earth Rotation Service] when required, and obeyed by national time
authorities. The current leap-second offset is automatically
propagated through the <<GPS>> system.
@@ -121,7 +126,7 @@
[[leapfile]] leapfile::
A local file containing the current <<leap second>> offset, typically
fetched from <<USNO>> or <<NIST>> and potentially needing updates
- near the very beginning of each half year. Normally retrieved
+ near the end of each half year. Normally retrieved
by a cron(1) job, but some varieties of <<refclock>> (notably
GPSes) update the same information during normal operation.
@@ -145,13 +150,13 @@
http://www.nist.gov/[National Institute of Standards and
Technology]. The civilian national time authority of the USA;
runs <<WWVB>>. Responsible for keeping U.S. civil time
- coordinated with international UTC time. NIST time tracks <<USNO>>
- time to within a few nanoseconds.
+ coordinated with UTC. Civil <<NIST>> and military <<USNO>>
+ time agree to within nanoseconds.
[[NTP-classic]] NTP Classic::
The original reference implementation of NTP by Dave Mills, later
- maintained by the Network Time Foundation. NTPsec forked from it
- on June 6th, 2015.
+ maintained by the Network Time Foundation. It is available at
+ http://www.ntp.org/ . NTPsec forked from it on June 6th, 2015.
[[nonce]] nonce::
An arbitrary number that may only be used once. a random or
@@ -195,16 +200,19 @@
In an NTP context, "the pool" is usually the
http://www.pool.ntp.org/en/[NTP Pool Project], a collection of
thousands of NTP servers accessible through DNS servers that hand
- out service addresses at random from the pool.
+ out "nearby" server addresses from the pool. These servers are
+ usually run by volunteers, and available via well-known DNS names.
-[[proventic]] proventic:: <<Mills-speak>> for "the transitive completion of the
- authentication relationship", defined in RFC 5906. Time is proventic
- if it is provided by a chain of time servers between which packets
- are authenticated and the chain reaches back to Stratum 1.
+[[proventic]] proventic:: <<Mills-speak>> for "the transitive
+ completion of the authentication relationship", defined in RFC 5906.
+ Time is proventic if it is provided by a chain of time servers
+ between which packets are authenticated and the chain reaches
+ back to Stratum 1.
[[refclock]] refclock::
Shorthand for a "reference clock", a primary time source. A computer
- with a refclock is implicitly Stratum 1.
+ with a refclock is implicitly Stratum 1. Examples include <<GPS>>
+ or <<time radio>> receivers, or even a master cesium clock.
[[stratum]] stratum::
A "stratum" is a layer in the hierarchy of time servers. a
@@ -212,8 +220,10 @@
a refclock is stratum 1; and a client served by a stratum N is
stratum N+1. Often capitalized, especially when referring to all
members of a stratum. While strata up to 15 are defined, it is
- unusual to see a public timeserver with stratum > 3, and thus
- almost all NTP clients are at Stratum 4 or lower.
+ unusual to see a public timeserver with stratum greater than 3,
+ and thus almost all NTP clients are at Stratum 4 or lower.
+ Notice that a 'lower' stratum is closer to the reference clock than
+ a 'higher'.
[[time-radio]] time radio::
A radio receiver specialized for picking up accurate time reference
@@ -230,14 +240,15 @@
[[truechimer]] truechimer::
<<Mills-speak>> for a timeserver that provides time believed good,
that is with low jitter with respect to UTC. As with a
- link#falseticker[falseticker], this is usually less a property of
+ <<falseticker>>, this is usually less a property of
the server itself than it is of favorable network topology.
[[USNO]] USNO::
http://www.usno.navy.mil/USNO[The United States Naval Observatory],
one of the two U.S. national time authorities and the source of the
U.S. military time reference, now delivered primarily by GPS
- signals. U.S. civil and military time agree to within nanoseconds.
+ signals. U.S. civil <<NIST>> and military <<USNO>> time agree to
+ within nanoseconds.
[[WWVB]] WWVB::
https://www.nist.gov/time-and-frequency-services/nist-radio-stations/wwvb[The
=====================================
docs/tf582_4.txt
=====================================
--- a/docs/tf582_4.txt
+++ b/docs/tf582_4.txt
@@ -1,38 +1,42 @@
= European Automated Computer Time Services =
-Several European countries use the following message data format:
-
-
-0000000000111111111122222222223333333333444444444455555555556666666666777777777
+The National Laboratories of many European countries provide
+time information in a standardised format, an ITU-R
+Recommendation (ITU-R TF583.4). Information is provided
+over a dial-up modem, with one 78-char segment every second.
+A description of the time code is available at
+https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dissemination-of-time-via-the-public-telephone-network/the-european-telephone-time-code.html
+
+The following countries have traditionally provided this service:
+Austria, Belgium, Germany, Italy, The Netherlands, Poland, Portugal,
+Romania, Spain, Sweden, Switzerland, Turkey and United Kingdom.
-0123456789012345678901234567890123456789012345678901234567890123456789012345678
+Note that the service is usually available from outside the country
+as well, as long as you are willing to make a long-distance phone
+call.
-This format is an ITU-R Recommendation (ITU-R TF583.4) and is now
-available from the primary timing centres of the following countries:
-Austria, Belgium, Germany, Italy, The Netherlands, Poland, Portugal,
-Romania, Spain, Sweden, Switzerland, Turkey and United Kingdom. Some
-examples are:
+Some examples are:
-* In Germany by Physikalisch-Technische Bundesanstalt (PTB)'s timecode
+* In Germany, Physikalisch-Technische Bundesanstalt (PTB)'s timecode
service. Phone number: +49 5 31 51 20 38.
+
For more detail, see
-http://www.ptb.de/cms/index.php?id=1786&L=1
+https://www.ptb.de/cms/index.php?id=1786&L=1
-* In the UK by National Physical Laboratory (NPL)'s Telephone Time Service.
+* In the UK, National Physical Laboratory (NPL)'s Telephone Time Service.
Phone number: 020 8943 6333
+
-For more detail, see http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/time-synchronisation-of-computers-to-utc(npl)
+For more detail, see https://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/time-synchronisation-of-computers-to-utc(npl)
-* In Italy by L'Istituto Nazionale di Ricerca Metrologica
+* In Italy, L'Istituto Nazionale di Ricerca Metrologica
(INRIM)'s CTD service. Phone numbers: 011 39 19 263 and 011 39 19 264
+
-For more detail, see http://www.inrim.it/res/tf/ctd_i.shtml
+For more detail, see https://www.inrim.it/res/tf/ctd_i.shtml
-* In Sweden by SP Swedish National Testing and Research Institute 's
+* In Sweden, SP Swedish National Testing and Research Institute's
timecode service. Phone number: +46 33 415783.
+
-For more detail, see http://www.sp.se/en/index/services/time_sync/modem_time/Sidor/default.aspx
+For more detail, see https://www.sp.se/en/index/services/time_sync/modem_time/Sidor/default.aspx
== Additional Information ==
View it on GitLab: https://gitlab.com/NTPsec/ntpsec/compare/8c0b96f059686805b57e8fdb13ccf90e5b8090d3...d98cd88896e9e7a00456594df459f6c93ce13042
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