Blue-sky thread - ideas for well after 1.0

[Daniel Franke]

There aren't many deficiencies in NTPv4 which can't be fixed by adding
extension fields. A change big enough to make a version bump
worthwhile would incorporate at least most of the following:

1. Drop everything other than client/server mode. Replace mode 6 with
something that runs over HTTPS on the NTS-KE port.

2. Let client and server packets be formatted differently. Achieve
data minimization by just taking the unnecessary fields out of client
packets altogether.

3. Forbid use of the legacy MAC field, thus fixing the hairiness
around extension parsing.

4. Make NTS mandatory. In the NTPv5 packet format, the version, mode,
NTS unique identifier, and (in client packets) NTS cookie come first
in plaintext, then the whole rest of the packet is encrypted.

5. Ditch the useless poll, stratum, refid, and reference timestamp
fields. Given that all of the above are implemented, origin timestamp
also becomes redundant (NTS takes the place of its anti-spoofing
role).

6. Represent timestamps as days, seconds, and fractions so that the
time can be represented unambiguously during leap seconds. Make the
day field 64 bits wide so that its range comfortable exceeds the
lifespan of the solar system.

7. Don't implement leap smearing in the wire protocol (servers should
always report accurate, unsmeared time), but standardize a formula for
translating NTP time into smeared UNIX time seen by other
applications.