Re: [Ntp] Leap second draft

[Kurt Roeckx <[e-mail]>]

On Fri, Mar 29, 2019 at 08:57:42PM +0100, Daniel Franke wrote:
> 3.  The Leap Data and Era Number extension field
> 
>    The Leap Data and Era Number extension field SHALL be formatted as
>    shown in Figure 1.
> 
>     0                   1                   2                   3
>     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |          Field Type           |            Length             |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |ELI|F|R|X| res |                   Era Number                  |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |                         TAI-UTC Offset                        |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |                                                               |
>    .                             Padding                           .
>    |                                                               |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> 
>          Figure 1: Leap Data and Era Number extension field format
> 
>    The fields are defined as follows:
> 
>       Field Type: MUST be set to [[TBD]].
> 
>       Length: The length of the extension field as specified by
>       [RFC7822].
> 
>       ELI: The Extended Leap Indicator, as specified below.
> 
>       F: When set, indicates that the Reference Timestamp was captured
>       during a leap second.
> 
>       R: When set, indicates that the Receive Timestamp was captured
>       during a leap second.
> 
>       X: When set, indicates that the Transmit Timestamp was captured
>       during a leap second
> 
>       res: These three bits are unused and reserved.  Senders MUST set
>       them to 0.  Receivers MUST igonre them.
> 
>       Era Number: The era, as defined in [RFC5905], during which the
>       Receive Timestamp was captured, given as an unsigned 24-bit
>       integer in network byte order.
> 
>       TAI-UTC Offset: The value DTAI as defined in [ITU.T4.1996],
>       expressed as a 32-bit signed two's-complement integer in network
>       byte order, as of the time reflected by the Receive Timestamp.  If
>       the Receive Timestamp is captured during a leap second, the given
>       TAI-UTC SHALL be as of just prior to the beginning of that leap
>       second.

In some other mail you wrote:
> However, I do note that the current draft implements only part of what
> I recommended, and I think it would be further improved by doing the
> rest of it as well. To reiterate what I recommended, in place of the
> current LEAP tag, provide the following three tags:
> 
> MRLS - a TAI timestamp representing the time at which the
> most-recently published leap second ends. This may be in either the
> future or the past.
> 
> LSDI - A bit indicating whether the leap second given in MRLS is an
> insertion or a deletion.
> 
> UTCO - What the TAI-UTC offset was or will be as of the time given
> in MRLS.

So I'm wondering why this MRLS is not part of this draft and that
ELI is 2 bits instead of the 1 bit LSDI.

Using that combination would at least avoid the comments about it
being possible to have a leap second every 1 or 6 months.


Kurt