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DHCP already has support for providing an NTP server IP; there has been at least one proposal[1] to also provide a DHCP option specifying the "rough current tim

DHCP already has support for providing an NTP server IP; there has been at least one proposal[1] to also provide a DHCP option specifying the "rough current time", so that devices have at least _something_ to start with. As for trust, you're already going to be trusting DHCP to give you an IP address, you could also trust it for this (with some safeguard in place to catch known-wrong values). This kindof reinforces how having an 'IoT Gateway' would be a good idea: The gateway can provide DHCP, and rough time, and (S)NTP, and DNS, and can also act as a proxy to the outside. [1]: http://www.potaroo.net/ietf/idref/draft-ogud-dhc-udp-time-option/ http://www.potaroo.net/ietf/idref/draft-ogud-dhc-udp-time-op...

tinus_hn 8y ago
Do you trust your local McDonalds with that kind of access?
- F_r_k 8y ago
  If you have no time information (i.e. no rtc), then yes
josteink 8y ago
> This kindof reinforces how having an 'IoT Gateway' would be a good idea: The gateway can provide DHCP, and rough time, and (S)NTP, and DNS Aka a router. Am I missing something?
- mschuster91 8y ago
  Yes, as routers generally only speak Ethernet and WiFi while IoT devices speak Zigbee, BT/LE, Powerline, 433 MHz custom protocols, a bunch of low power WAN protocols and for the more professional/industry settings CANbus, Profibus and more.
  - josteink 8y ago
    AFAIK Powerline is Ethernet, so that’s covered. Zigbee, BT/LE, 433Mhz and friends don’t do IP, so they won’t need DHCP and DNS. So again... What am I missing?
  - deleted 8y ago
    [deleted]
- gumby 8y ago
  I doubt most routers provide DHCP. Maybe consumer ones.
  - detaro 8y ago
    What's the point of this nitpick? Networks that configure everything statically are fairly rare, and do so intentionally. If they don't, they have a DHCP server somewhere already, and if they aren't consumer-level networks they sure as hell don't want some random "IoT gateway" box providing DHCP. So it's clear what "router" means in this context.
    - gumby 8y ago
      I have a separate dhcp server so if the router has issues machines can still attach to the network and talk to local services.
  - p1necone 8y ago
    In my experience the majority (all the ones I've owned at least) of consumer grade routers have DHCP.
  - psds2 8y ago
    Most layer 3 switches provide DHCP, and since almost all consumer routers also provide DHCP, probably most routers do provide DHCP.
Fnoord 8y ago
Next post: "Why You Can't Trust DHCP"
m463 8y ago
I run NTP at home, using an inexpensive USB GPS dongle as the time source. Unfortunately it's technically challenging to create a configuration to use it in a meaningful way, especially when the system reboots. Really what you need is a process to bring up the GPS, wait until the time is up and reliable, then set the hardware clock and launch NTP "correctly" (without falsetickers and all the other ntp convergence nonsense)
- nineteen999 8y ago
  I run NTP at work, more specifically, we use GPS time sources to synchronize a wide-area paging network (by wide area I mean over an area nearly a quarter of a million km square). Timing is extremely critical for our application to work correctly over an area that size. The only viable option for us is about 3 (or more) rackmount NTP appliances from a well known vendor which have the GPS already integrated, support for multiple time source modules and power supplies, and have integrated software to drive the whole thing. This means we need to get GPS antennas installed on the roof of the datacenter and fiber run from there to our racks. Our remote sites (connected by 4G and VSAT) also have GPS units, but they are connected via RS-232 serial (not USB) and suffer from some of the synchronization issues you describe. They fallback to the time servers in the datacenters in the event that the local GPS time source is rejected.
  - ncmncm 8y ago
    Hmm, a quarter million km square really would be a wide area: 62 billion square km, or just about the surface area of Jupiter, if Jupiter had a proper surface. A quarter million square km seem more plausible.
    - nineteen999 8y ago
      Well I'd like to tell you it was the former, but in truth our paging transmitters aren't powerful enough to reach Earth from Jupiter. Thank you for pointing out my typo.
      - 8y ago

tinus_hn 8y ago

Do you trust your local McDonalds with that kind of access?

F_r_k 8y ago
If you have no time information (i.e. no rtc), then yes

josteink 8y ago

> This kindof reinforces how having an 'IoT Gateway' would be a good idea: The gateway can provide DHCP, and rough time, and (S)NTP, and DNS Aka a router. Am I missing something?

mschuster91 8y ago
Yes, as routers generally only speak Ethernet and WiFi while IoT devices speak Zigbee, BT/LE, Powerline, 433 MHz custom protocols, a bunch of low power WAN protocols and for the more professional/industry settings CANbus, Profibus and more.
- josteink 8y ago
  AFAIK Powerline is Ethernet, so that’s covered. Zigbee, BT/LE, 433Mhz and friends don’t do IP, so they won’t need DHCP and DNS. So again... What am I missing?
- deleted 8y ago
  [deleted]
gumby 8y ago
I doubt most routers provide DHCP. Maybe consumer ones.
- detaro 8y ago
  What's the point of this nitpick? Networks that configure everything statically are fairly rare, and do so intentionally. If they don't, they have a DHCP server somewhere already, and if they aren't consumer-level networks they sure as hell don't want some random "IoT gateway" box providing DHCP. So it's clear what "router" means in this context.
  - gumby 8y ago
    I have a separate dhcp server so if the router has issues machines can still attach to the network and talk to local services.
- p1necone 8y ago
  In my experience the majority (all the ones I've owned at least) of consumer grade routers have DHCP.
- psds2 8y ago
  Most layer 3 switches provide DHCP, and since almost all consumer routers also provide DHCP, probably most routers do provide DHCP.

Fnoord 8y ago

Next post: "Why You Can't Trust DHCP"

m463 8y ago

I run NTP at home, using an inexpensive USB GPS dongle as the time source. Unfortunately it's technically challenging to create a configuration to use it in a meaningful way, especially when the system reboots. Really what you need is a process to bring up the GPS, wait until the time is up and reliable, then set the hardware clock and launch NTP "correctly" (without falsetickers and all the other ntp convergence nonsense)

nineteen999 8y ago
I run NTP at work, more specifically, we use GPS time sources to synchronize a wide-area paging network (by wide area I mean over an area nearly a quarter of a million km square). Timing is extremely critical for our application to work correctly over an area that size. The only viable option for us is about 3 (or more) rackmount NTP appliances from a well known vendor which have the GPS already integrated, support for multiple time source modules and power supplies, and have integrated software to drive the whole thing. This means we need to get GPS antennas installed on the roof of the datacenter and fiber run from there to our racks. Our remote sites (connected by 4G and VSAT) also have GPS units, but they are connected via RS-232 serial (not USB) and suffer from some of the synchronization issues you describe. They fallback to the time servers in the datacenters in the event that the local GPS time source is rejected.
- ncmncm 8y ago
  Hmm, a quarter million km square really would be a wide area: 62 billion square km, or just about the surface area of Jupiter, if Jupiter had a proper surface. A quarter million square km seem more plausible.
  - nineteen999 8y ago
    Well I'd like to tell you it was the former, but in truth our paging transmitters aren't powerful enough to reach Earth from Jupiter. Thank you for pointing out my typo.
    - 8y ago