[time-nuts] Serial or other simple protocols for exchanging time

[Bob kb8tq]

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 <hmurray at megapathdsl.net> wrote:
> 
> 
> ausserirdischesindgesund at gmail.com 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 -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.