[ntp:questions] Re: How to handle leap second condition correctly?

David L. Mills mills at udel.edu
Sun Jun 12 15:59:24 UTC 2005


The legal values for stratum in rfc-1305 are 1-255 (see page 10). 
Stratum 0 is intended as unknown or invalid. Strata 15 or 16 have no 
particular interpretation other than as convention in the reference 
implementation.  However, if a count-to-infinity hazard exists, use of 
strata greater than a "small" number could be dangerous. That's why I 
suggested strata 1-14 in rfc2030 for primary and secondary with 15-255 
as reserved. The value 14 should be 15 to match the reference 
implementation, but any choice is arbitrary. The point is that some 
choice of "infinity" is necessary with the expectation that, should the 
stratum equal or exceed infinity be mapped to zero.

Any distinction between NTP and SNTP with regard the on-wire protocol is 
  misguided. They use the same protocol. My suggestion of default values 
was intended to simplify the operation while preserving the same 
timestamp calculations.


Harlan Stenn wrote:
> Dave,
> I just re-read the draft 2030 spec and it says that the legal values for
> stratum on a reply are 1-14.
> 0 is a KOD reply.  If an SNTP implementation is not sync'd to a refclock
> I see no clear statement in the draft RCF that it should return a KOD reply.
> I also do not understand why 15 is not listed as an allowed value in a
> stratum response.  I would expect 15 to be returned from a sender at stratum
> 14.
> Also, the draft SNTP RFC says:
>  Stratum: This is a eight-bit unsigned integer indicating the stratum of the
>  server or client, with values defined as follows:
>    Stratum  Meaning
>    ----------------------------------------------
>    0        kiss-o'-death message (see below)
>    1        primary reference (e.g., synchronized by radio clock)
>    2-15     secondary reference (synchronized by NTP or SNTP)
>    16-255   reserved
> The following seems better to me:
>    Stratum  Meaning
>    ----------------------------------------------
>    0        kiss-o'-death message (including SNTP client.  See below)
>    1        primary reference (NTP or SNTP, synchronized, e.g., by radio clock)
>    2-15     secondary reference (synchronized by NTP)
>    16-255   reserved
> I gather the IETF WG is the place to go over this stuff.
> H

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