Re: [Ntp] Finding leap-seconds.list


On 8 Nov 2018, at 2:17, Denis Reilly wrote:

> Thomas and Martin,
>
> On doing my own research into this for the BCP, I found that the Time 
> Zone database maintenance procedures are documented in BCP 175 / RFC 
> 6557.
>
> However, after the discussion during the WG meeting, I think it's 
> better to remove the mention of the leap second file hosted by the 
> IETF in the BCP. As Martin notes, there are better places to get it.
I agree with Denis.

>
> --
> Denis Reilly  |  Technical Lead  |  denis.reilly@orolia.com  
> (585)321-5837
>
> -----Original Message-----
> From: ntp <ntp-bounces@ietf.org> On Behalf Of Martin Burnicki
> Sent: Wednesday, November 07, 2018 1:00 PM
> To: Thomas Peterson <hidinginthebbc@gmail.com>; ntp@ietf.org
> Cc: Paul Eggert <eggert@cs.ucla.edu>
> Subject: Re: [Ntp] Finding leap-seconds.list
>
> Thomas Peterson wrote:
>> As was discussed at the working group meeting at IETF 103 [0], I have 
>> decided to do some research on the leap-seconds.list file that the 
>> IETF appears to be hosting at 
>> https://www.ietf.org/timezones/data/leap-seconds.list, but for some 
>> participants of this working group appear unclear about.
>
> During the IETF NTP WG session I posted a link in the chat which 
> points to a PDF I wrote some time ago:
> https://www.meinbergglobal.com/download/burnicki/the_ntp_leap_second_file.pdf
>
> There are several "original" versions of that file published by the 
> IERS, NIST, and USNO.
>
> One of those original files (usually the version from NIST) is used to 
> update the TZDB records, and the original file is also included in the 
> TZDB distribution/tar ball, which is then unpacked and made available 
> at the IETF web site.
>
> The problem here is that first an update of the original leap second 
> file appears, and only whenever the next TZDB version is released 
> after that the file appears on the IETF web site.
>
> So for most users it's better to pick up a file from one of the 
> original sites.
>
>> Where is this referenced in an RFC or other IETF document?
>> I ran a search of “leap-seconds.list” across the spread of draft 
>> and RFC documents. No RFC that I have found makes direct reference. 
>> However, the current NTP BCP draft Section 4.6 [1] contains:
>>
>> ... SNIP ...
>>
>> The IETF maintains a leap second list [[7]] for NTP users who are not
>>    receiving leap second information through an automatic source.
>>
>>    Files are also available from other sources:
>>
>> ... SNIP ...
>>
>> With [[7]] holding reference to the file hosted at, and a list of 
>> links to sources.
>>
>> What else is www.ietf.org hosting of a similar nature?
>> This file alone is not the only thing hosted under www.ietf.org, in 
>> fact https://www.ietf.org/timezones/ directory listings show that all 
>> recent versions of the tzdb (including 2018g the most recent) which 
>> suggests a human maintaining the hosting of it, or automated process. 
>> Versions only go back to 2016. These files are also available over 
>> FTP [2].
>>
>
> Yes, and since the leap seconds file is part of the TZDB, it also 
> becomes available via the IETF web site.
>
>> How long have these files been hosted on www.ietf.org?
>> Internet archive's Wayback Machine [3] shows it appearing back in 
>> 2015.
>>
>> Who is using the file?
>> ntpd does depend on it as was discussed at the WG meeting, [4]. 
>> FreeBSD [5] holds reference to it and users have reported issues when 
>> being unable to access it in the past. In addition, at least one 
>> library [6] make use of it outside of ntpd, however I don't believe 
>> this is heavily used or cause non-developers or system administrators 
>> any pain if it went missing.
>
> I'm sure the file *is* heavily used, but maybe not directly from the 
> IETF web site.
>
> It's a good source to become aware of an upcoming leap second, and 
> it's a good source to be able to determine the current UTC/TAI offset, 
> as e.g. required when using PTP which uses TAI timestamps by default.
>
> Anyway, I think the file is mostly used by NTP or PTP servers since 
> for most applications the information interesting for clients can be 
> passed via the individual protocols.
>
>
> Regards,
>
> Martin
> --
> Martin Burnicki
>
> Senior Software Engineer
>
> MEINBERG Funkuhren GmbH & Co. KG
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