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by simoncion 801 days ago
> It would be nice if DHCP could provide the current time as one of the pieces of information it provides with a lease. [0]

DHCP can provide the IP address of one or more NTP servers to consult for time queries. I use this feature so that all of the machines on my LAN (at least the ones that can be configured to ask for and/or use this information) have the same general idea of what time it is.

[0] See subsection 8.3 here: <https://www.rfc-editor.org/rfc/rfc2132#section-8>
1 comments
magicalhippo 801 days ago
I do that, with a local GSP-synced Pi. Very cheap and easy to set up with IPv4 at least.

That said, if you don't trust the DHCP server because some evil actor might give you the wrong time, why should you trust the NTP server it tells you about?

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simoncion 801 days ago
I agree that if you distrust the network operator (but must use the operated network for some reason) that you should accept as little configuration information provided by that operator as is reasonably possible.

That goes without saying.

I mentioned the fact that DHCP can provide NTP server information as a way to explain why DHCP wouldn't just straight-up provide "current time" information. Why do that when you can point people to a server running a far superior purpose-built timekeeping protocol? It'd just be silly to do the worse thing.

(Notice also that RFC2132 was published in 1997. In my mind, this moots any retorts that a good reason for providing time directly would be because the DHCP server's supplicant is too underpowered to run an NTP client. In 2024? On a consumer-grade device? No way.)

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magicalhippo 801 days ago
Oh yeah, certainly agree. Especially since devices can use SNTP[1] to talk to a NTP server if they just want to know the current time and don't need all the complexity of NTP.

[1]: https://timetoolsltd.com/ntp/sntp-overview/

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