Bob, ntpd for ages has supported broadcast/multicast UDP. https://www.eecis.udel.edu/~mills/ntp/html/assoc.html#broad
If you care about security it's like a bag of angry cats. And the one-way-ness removes the ability to measure round-trip delay. So it's pretty rare to see it being used well. Tim N3QE On Thu, Aug 15, 2019 at 11:08 AM Bob kb8tq <[email protected]> wrote: > Hi > > Which all sort of begs the question: > > Why not a simple “broadcast UDP” once a second time packet approach for a > home LAN? > > Unless you get really crazy, it’s not going to be a very big packet. > Seconds since some > arbitrary point in time. Time zone offset. Maybe a leap second count. > Server ID maybe. > Less than 100 bytes not including the overhead. > > Bob > > > On Aug 15, 2019, at 5:36 AM, Hal Murray <[email protected]> wrote: > > > > > > [email protected] said: > >> I am a newbie and am wondering what options there are for exchanging > time > >> on a more basic level than NTP or PTP (that is for situations when a > >> full network stack is too complex). > > > > You haven't described your problem fully yet. > > > > Are you interested in client side or server side? (or both) > > > > What sort of environment are you working in? What sort of hardware do > you > > have available? > > > > NMEA over a serial port is probably what you want, but... > > > > > > Raspberry Pi and similar are not very expensive. They come with > networking > > software. The Pi isn't very nice for time-nut work over the net because > the > > Ethernet is on USB which adds jitter and/or hanging bridges. It does > have > > GPIO. > > > > > > There is a lot of things you can do without a "full network stack". > > > > What level of hacking is reasonable depends on your environment. For a > setup > > at home, you are unlikely to annoy anybody else. > > > > The Alto firmware could boot over the (3 MB) Ethernet. The boot servers > would > > periodically send a boot-loader packet to a reserved hardware address. > The > > firmware only had to setup the hardware to receive a packet, wait for > one, > > sanity check things, and jump to it. > > > > If you use UDP rather than TCP, the "stack" level packet format is much > > simpler. Retransmission becomes trivial if you only have one un-ACKed > packet > > to consider. Performance on a LAN is OK most of the time. > > > > For something like a NTP server, you can avoid routing and ARP by > sending the > > reply back where it came from. > > > > For the client side, the normal problem is finding the server. If you > only > > have one server, you can wire in the address. > > > > > > > > > > -- > > These are my opinions. I hate spam. > > > > > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
