Hi Giovane, a time server is a required DHCP option for DOCSIS devices. This uses the older TIME protocol (UDP port 37, RFC 868). However, it's common for DOCSIS devices like MTAs, STBs, etc to also request and use NTP server addresses received via DHCP (they may apply this using SNTP rather than a fully fledged NTP client). As one data point, Google Fiber (a large GPON based ISP in USA) provides NTP servers to customers via DHCP. We actually had to contact them as they were providing a set of server addresses where one or more of the servers was no longer reachable. Some of our VoIP telephones used by employees did not like receiving bad info and would intermittently fail to register. Google Fiber was able to remove the bad info from their DHCP replies. We've seen some similar behavior in other networks so now I believe we prefer to ignore/override the DHCP provided NTP info with known good server addresses (it seems too common for NTP to simply be ignored/overlooked by network operators and users). --Blake On 10/1/2021 9:12 AM, Giovane C. M. Moura via NANOG wrote:
hello folks,
So DHCP can also be used to set NTP servers on clients, for both IPv4[rfc2132] and IPv6[rfc5908].
I'm looking for statistics on setting NTP servers on clients using DHCP, in the wild. Does anyone know if there is any available somewhere?
I'm also looking for reports from operators and their experiences on this, and why they use (or not) this DHCP feature, and what types of networks is this deployed, and their motivations, etc.
Thanks in advance,
/giovane