[ntp:questions] NIST vs. pool.ntp.org ?

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Wed Mar 27 20:40:28 UTC 2013


Robert Scott wrote:
> I am confused about the proper usage of pool.ntp.org and NIST.

NIST isn't of much value outside the continental US,
 other regional equivalent national time and frequency
 standards closer to the point of usage should have much
 greater value for those that run Stratum One NTP Servers.

 Regional / National / Country time & frequency standard services
  typically have cesium beam atomic clocks, hydrogen maser atomic clocks,
  caesium fountain atomic clocks, rubidium gas cells, ...

 e.g. Places like these <http://en.wikipedia.org/wiki/Radio_clock>
 CSIRO National Measurement Laboratory, Melbourne & Sydney, Australia
 Canadian Meteorological Centre, Dorval, Québec, Canada
 Integrated Systems Laboratory, Swiss Fed. Inst. of Technology, Zurich, Switzerland
 CSTV of National Research Council, Torino, Italy
 New Delhi, National Physical Laboratory of India
 National Institute of Information and Communications Technology, Tokyo, Japan
 SP Swedish National Testing and Research Institute, Boras, Sweden
 NPL Time and Frequency Services National Physical Laboratory Middlesex UK
 NIST National Institute of Standards and Technology US
 ...

NIST (and other national equivilants) are usually used by Stratum One Servers
 {that have Local Stratum Zero Reference clocks, e.g. GPS}
 that provide NTP service to many (hundreds ?) of clients
 e.g. Corporate NTP servers providing service to their LAN clients,
  College NTP servers providing service to classroom and dorm clients,
  ...


> pool.ntp.org seems to be a collection of private sector
>  time servers offered for all to use, but with registration
>  expected for regular users.

The Vendor Pool? <www.pool.ntp.org/en/vendors.html>
 That is due to the several vendors   (NetGear, SMC, DLink, Tardis)
  who (unintentionally) had poor implementations / bugs in their
  ntp code that hammered ntp server farms to death.
 e.g. <http://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse>

It allow them to more easily identify (and hopefully contact)
 a source of abuse, as well as being able to shift or spread
 the source of abuse to prevent it from DDOS taking down
 NTP servers, Networks, ISPs, ...


> the round-robin address of time.nist.gov does not seem to return anything.

Sound like you are not dealing with CNames correctly?

Question:
   Name=time.nist.gov, QTYPE=A, QCLASS=1
Answer Section:
- Name=time.nist.gov
    Type=CNAME, Class=1, TTL=1145 (19 Minutes 5 Seconds), RDLENGTH=10
    CNAME=ntp.glb.nist.gov
- Name=ntp.glb.nist.gov
    Type=A, Class=1, TTL=101 (1 Minute 41 Seconds), RDLENGTH=4
    IP Address=216.171.120.36


Question:
   Name=time.nist.gov, QTYPE=A, QCLASS=1
Answer Section:
- Name=time.nist.gov
    Type=CNAME, Class=1, TTL=777 (12 Minutes 57 Seconds), RDLENGTH=10
    CNAME=ntp.glb.nist.gov
- Name=ntp.glb.nist.gov
    Type=A, Class=1, TTL=518 (8 Minutes 38 Seconds), RDLENGTH=4
    IP Address=64.236.96.53


Question:
   Name=time.nist.gov, QTYPE=A, QCLASS=1
Answer Section:
- Name=time.nist.gov
    Type=CNAME, Class=1, TTL=746 (12 Minutes 26 Seconds), RDLENGTH=10
    CNAME=ntp.glb.nist.gov
- Name=ntp.glb.nist.gov
    Type=A, Class=1, TTL=598 (9 Minutes 58 Seconds), RDLENGTH=4
    IP Address=128.138.141.172


...


> ...I saw the NIST servers that did not seem to be part of the pool.

Many (but not all) are.  {I see them in there all the time.}

For a brief test, set your floor to 1,
 and it will be easier for you to notice them.


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