The Report of the URSI Commission J Working Group on the Leap Second read:

Appendix III. "Standard Reply" to queries concerning the questionnaire

The response one person sent me is below, and it concerns Network Time Protocol (NTP), which uses the internet to transfer time.

...

If leap seconds went away, the NTP community would worship the ground you walk on. Leap secs introduce a manual discontinuity in the NTP time scale. It takes a while to propagate leap secs through the hierarchy.

While I concur on the unfortunate way in which NTP time stamps are encoded, I was running a sub-tree of NTP servers on an ado "right_only" system back in 1989 that, with the addition of a single time2posix() call, sailed through leap seconds without a hiccup (and without the need for any leap-second warning), so, I would proffer that leap seconds are not as much of a problem for NTP as many people seem to believe. Of course, leap-second warnings need to be replaced with the timely distribution of new ado zoneinfo data (which would also help with the ever changing summertime rules). I'm surprised that after all these years we do not have such a system in place, even if it was just a new DNS record type tied to names like New_York.America.zoneinfo.org. Bradley