On 2017-11-02 19:54, Daniel Ford wrote:
Zefram,
Ah yes, I'd forgotten about the 'version' file; definitely the way to check for updates.
Thanks for the clarification about the zone1970.tab contents. So maybe I can program the clock to make a once-only access to a TZdb mirror for that file, at first start-up, to fetch the region/cities list for the owner to choose from. If something ever changed to make that choice invalid, there could be a service routine in the firmware that allowed the user to re-do this once-only download for a new region/city selection. (Whew, things are getting complicated! :-)
But the most exciting part of your e-mail was the mention of the IETF working group! I went there and found that they had concluded their work and issued RFC7808. I downloaded that and read it, and think that the "expand" Action is just what I'm looking for! So all I need to do is find one or more TZDIST servers that look like they should be around for the long-term.
Embedded devices must have some way of changing server names otherwise they risk becoming useless junk by the time they are built, or an annoying irritant to parts of the Internet, which may have legal, financial, social, and reputational risks. See https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse#Notable_cases
To my (simple) way of thinking, it would make sense if (some) NTP servers added this TZDIST functionality, so they became a 'one-stop-shop' for current time information, but whether they have/will is another matter. I'll start looking.
If the servers require TLS aka SSL, and maybe also DNSSEC, that may increase the requirements for an Arduino implementation to 32 bit AVR with lots of storage and Wifi shield with DNS, HTTP, HTTPS, SSL support. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada