David J Taylor wrote: > "David J Taylor" > <david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in > message news:%xqgm.126$ym4...@text.news.virginmedia.com... > >> "Unruh" <> wrote in message news:34jgm.50898$ph1.36...@edtnps82... >> [] >> >>> Note that chrony will give you a factor of 2 or three improvement over >>> ntp in the errors, assuming that the roundtrip is equally split on >>> Linux or BSD. >>> True but it doesnt support AutoKEY operations so it has no value in provable time settings which are now key requirements in many commercial settings. >> For those without wide-bandwidth academic connections - those folks on >> cable or ADSL - how good is an "equal split round trip" assumption? >> >> David >> David - This doesnt take into account the issues of peering agreements and backhauling which add a non-deterministic type of latency to the time-setting process as does the peering agreements between the various carriers who's networks the time-service providers systems operate in. It also takes into account system I/O latency's and the issues of time-provider or infrastructure loading.
Also most parties using cable networks are probably running home gear with SNTP enablement in most instances. Its unlikely that a NTP client exists in most sub-$100 infrastructure devices. I think the answer is that no one knows and it could be as little as a few milliseconds or it could be more and we wont know. It also depends on whether the time server those client systems are tied to are located on the Open Internet or are operated by the Cable Providers for their clients use. Then the secondary non-deterministic impulse and the asymmetric routing delays are mitigated or eliminated so again - it depends on how NTP is being used and whether its a real NTP instance or just a SNTP instance (as it exists today) being used. > > Thanks, David, David and Jan. A few milliseconds is what I had expected, > so if you are on a consumer line, what implications does that have for > unruh's comment? > > Cheers, > David > > _______________________________________________ > questions mailing list > questions@lists.ntp.org > https://lists.ntp.org/mailman/listinfo/questions > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.423 / Virus Database: 270.14.39/2470 - Release Date: 10/30/09 > 15:18:00 > > _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions