[LEAPSECS] DNS examples

[Rob Seaman]

On Jan 24, 2015, at 7:27 AM, Rob Seaman <seaman at noao.edu> wrote:

> As shown, I think we also want to index TAI-UTC after the leap.  This is similar to how the IERS table has it, and remaining aligned with that resource may be a strong enough argument.  (Negative leap seconds would also be made pretty obvious as values above 128 in the third byte.)
> 
> Have also added a frame forward from leapsec.com to http://hpiers.obspm.fr/iers/bul/bulc/Leap_Second_History.dat for easy browser access.
> 
> If there are no strong objections I'll write an encoder/decoder for the rearranged format and update DNS as described.

Here's a go at the new encoding.  I haven't updated the DNS yet pending feedback.  If the first byte is >= 248 you can see immediately that the entry corresponds to a leap second.  The second byte increments monthly and cycles after a couple of decades or so.  The third byte is TAI-UTC applicable from the start of the month in question (or before).

If we don't hit a negative leap second in the next few decades, the baseline LOD should have grown such that this will never happen.  In that case the range of the third byte above 128 should be available for more positive leap seconds.  That is, the speed-up during the middle ages was a couple of milliseconds.  If the baseline is greater than a repeat of such an event positive leap seconds will continue to accumulate - in addition to the leverage of the growing tally itself.  Or to put it another way, if leap seconds start to arrive more quickly this version of the format will naturally accommodate the need through its 2142 lifetime.

Rob
--

YYYY MM before  after  encoded crc         IP              Decoded         flags
--------------------------------------------------------------------------------
2005  1     32     32 f18c2000  19  241.140. 32. 25 -> OK  2005  1  32  0  (0, 0)
2005  7     32     32 f1922000  6a  241.146. 32.106 -> OK  2005  7  32  0  (0, 0)
2006  1     32     33 f9982100  e9  249.152. 33.233 -> OK  2006  1  33  1  (1, 0)
2006  7     33     33 f19e2100  be  241.158. 33.190 -> OK  2006  7  33  0  (0, 0)
2007  1     33     33 f1a42100  b1  241.164. 33.177 -> OK  2007  1  33  0  (0, 0)
2007  7     33     33 f1aa2100  2e  241.170. 33. 46 -> OK  2007  7  33  0  (0, 0)
2008  1     33     33 f1b02100  66  241.176. 33.102 -> OK  2008  1  33  0  (0, 0)
2008  7     33     33 f1b62100  8f  241.182. 33.143 -> OK  2008  7  33  0  (0, 0)
2009  1     33     34 f9bc2200  a1  249.188. 34.161 -> OK  2009  1  34  1  (1, 0)
2009  7     34     34 f1c22200  a5  241.194. 34.165 -> OK  2009  7  34  0  (0, 0)
2010  1     34     34 f1c82200  01  241.200. 34.  1 -> OK  2010  1  34  0  (0, 0)
2010  7     34     34 f1ce2200  e8  241.206. 34.232 -> OK  2010  7  34  0  (0, 0)
2011  1     34     34 f1d42200  a0  241.212. 34.160 -> OK  2011  1  34  0  (0, 0)
2011  7     34     34 f1da2200  3f  241.218. 34. 63 -> OK  2011  7  34  0  (0, 0)
2012  1     34     34 f1e02200  30  241.224. 34. 48 -> OK  2012  1  34  0  (0, 0)
2012  7     34     35 f9e62300  fe  249.230. 35.254 -> OK  2012  7  35  1  (1, 0)
2013  1     35     35 f1ec2300  e4  241.236. 35.228 -> OK  2013  1  35  0  (0, 0)
2013  7     35     35 f1f22300  97  241.242. 35.151 -> OK  2013  7  35  0  (0, 0)
2014  1     35     35 f1f82300  33  241.248. 35. 51 -> OK  2014  1  35  0  (0, 0)
2014  7     35     35 f1fe2300  da  241.254. 35.218 -> OK  2014  7  35  0  (0, 0)
2015  1     35     35 f2042300  48  242.  4. 35. 72 -> OK  2015  1  35  0  (0, 0)
2015  7     35     36 fa0a2400  98  250. 10. 36.152 -> OK  2015  7  36  1  (1, 0)