I'd suggest VMs are fine as a time source as long as they also sync from something else AND you're aware of how your hypervisor impacts time keeping and allow for that.
On Tue, 14 July 2026, 7:56 am Mark Smith, <[email protected]> wrote: > Going from the news reports they only had two. > > Two services ir devices for redundancy is usually enough. > > That's what I thought about NTP, until I read the following BCP. > > The ideal minimum number of NTP time sources for a client is *5*, due to > the way time sources are compared to try to identify the best and most > accurate one to follow, and then to have redundancy, which comes with > having an odd number of NTP sources. > > RFC8633, "Network Time Protocol Best Current Practices" > https://datatracker.ietf.org/doc/html/rfc8633 > > > Also, don't use VMs as NTP time servers. The underlying virtualisation > layer can cause the VM's virtual timer interrupt to drift about. > > You want a hardware timer interrupt to be driving the OS's clock. > > If Telstra had had 5 Stratacom NTP servers, even if they were all old and > had the 20 years ago time fault, it's possible that due to different power > on times, the first one that failed and turned time back 20 years would > have been ignored by the others and clients because it became a bad time > source, and they may have been lucky enough to have time to mitigate the > remaining ones failing before it had an impact. > > > Regards, > Mark. > > On Tue, 14 July 2026, 15:30 Luke Thompson, <[email protected]> wrote: > >> "Telstra had a nation-wide network outage last week that affected >> emergency services. >> >> The outage has been pinned on an obsolete Symmetricom SyncServer S300 >> node, which manages time on the network but resets its 10-bit week counter >> to zero every 1024 weeks (just under 20 years) in a common and well >> understood GPS rollover bug that caused the device to reset to 2006. >> >> The SyncServer S300 was discontinued in 2016." >> >> Cheers, >> >> Luke Thompson, CTO >> The Network Crew P/L >> >> E: [email protected] >> https://tnc.works >> >> On 9 July 2026 7:21:52 am Greg Price <[email protected]> wrote: >> >>> The stuff I've read and heard is that it was a software update across >>> multiple systems that provide the reference sources from GNSS that went >>> wrong causing the the reference date/time to jump back decades, and the >>> wheels fall off. This is from the patchwork of sources, but I'd like to >>> hear it definitively from engineers. >>> >>> On 9 Jul 2026, at 7:12 am, Phillip Grasso <[email protected]> >>> wrote: >>> >>> Do you think it was related to software patching breaking time services? >>> (NTP?) >>> >>> On Wed, 8 July 2026, 2:48 pm DaZZa, <[email protected]> wrote: >>> >>>> To paraphrase an oft-repeated meme >>>> >>>> It's not NTP >>>> There's no way it's NTP >>>> It was NTP >>>> >>>> Bets on this just being a speculator to take the heat off until they >>>> find out what really went wrong? >>>> >>>> D >>>> >>>> On Wed, 8 Jul 2026 at 14:34, Luke Thompson <[email protected]> wrote: >>>> > >>>> > Telstra's CFO has pointed to time / NTP: >>>> > >>>> > >>>> https://www.theguardian.com/australia-news/2026/jul/08/telstra-outage-down-network-mobile-outages-today >>>> > >>>> > Seems just over 4 hours of impact, and so far they're unsure what >>>> caused it. >>>> > >>>> > Cheers, >>>> > >>>> > Luke Thompson, CTO >>>> > The Network Crew P/L >>>> > >>>> > E: [email protected] >>>> > https://tnc.works >>>> > >>>> > On 8 July 2026 8:43:01 am Luke Thompson <[email protected]> wrote: >>>> > >>>> >> & likewise, service restored at the moment. >>>> >> >>>> >> Cheers, >>>> >> >>>> >> Luke Thompson, CTO >>>> >> The Network Crew P/L >>>> >> >>>> >> [email protected] >>>> >> https://tnc.works >>>> >> >>>> >> >>>> >> On 8/7/2026 8:40 am, [email protected] wrote: >>>> >>> >>>> >>> Good morning >>>> >>> >>>> >>> Back here. Regional Vic Boost and T prepaid mobile data. >>>> >>> >>>> >>> ----- Original message ----- >>>> >>> From: [email protected] >>>> >>> To: [email protected] >>>> >>> Subject: [AusNOG] Telstra outage? >>>> >>> Date: Wednesday, 8 July 2026 7:44 AM >>>> >>> >>>> >>> G'day. >>>> >>> >>>> >>> How is T where you are? >>>> >>> >>>> >>> Regional Vic Boost network no calls other than emergency can be >>>> made. >>>> >>> >>>> >>> Cheers >>>> >>> Laurie >>>> >>> >>>> >> _______________________________________________ >>>> >> AusNOG mailing list >>>> >> [email protected] >>>> >> https://lists.ausnog.net/mailman/listinfo/ausnog >>>> > >>>> > >>>> > _______________________________________________ >>>> > AusNOG mailing list >>>> > [email protected] >>>> > https://lists.ausnog.net/mailman/listinfo/ausnog >>>> _______________________________________________ >>>> AusNOG mailing list >>>> [email protected] >>>> https://lists.ausnog.net/mailman/listinfo/ausnog >>>> >>> _______________________________________________ >>> AusNOG mailing list >>> [email protected] >>> https://lists.ausnog.net/mailman/listinfo/ausnog >>> >>> >>> >> _______________________________________________ >> AusNOG mailing list >> [email protected] >> https://lists.ausnog.net/mailman/listinfo/ausnog >> > _______________________________________________ > AusNOG mailing list > [email protected] > https://lists.ausnog.net/mailman/listinfo/ausnog >
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