Hi One really big thing that has changed is the number of folks doing this sort of thing via a dsl or cable modem that has > 20 ms of asymmetry. You will not find many NTP papers studying that sort of network connection.
Bob > On Dec 15, 2021, at 11:30 AM, Lux, Jim <[email protected]> wrote: > > On 12/15/21 7:53 AM, Magnus Danielson via time-nuts wrote: >> Hi, >> >> Expect network routes to be more dispersed these days, as it is needed. >> >> While the wedge plot is a classic for NTP, it may be interesting to plot >> forward and backward path histograms independently. >> >> Cheers, >> Magnus > > > I assume someone, somewhere has run some recent tests and maybe published > them. All those plots and behaviors from the early days of NTP might have > significantly changed, due to the plethora of new kinds of network routes. > Two things strike me as being "very different" from, say, 10-20 years ago - > 20 years ago, most routers were "store and forward" - the entire packet would > be received, and then decoded, and sent onward. These days, many routers > start sending the packet to the destination before the entire packet has been > received. To do S&F would take too much memory with multi Gbps speeds and > long packets. I recall being at a conference at least 10 years ago where > they were talking about the sophistication required in 10G routers - cut > through routing, adaptive equalization, etc. > > The other thing that has changed is a modern diversity of kinds of networks. > 20 years ago, it was basically wired connections of some kind with > concentrators/deconcentrators/switches/routers - all of which have moderately > well defined latency and statistics. > > Now, though, there's a lot of over the air (cell phones, WISP, 5,6,7G > nanocells injected surreptitiously - at least my neighbor claims that's what > they're doing). The latency on a WiFi connection, in a busy environment - > It's 8PM, and all the neighbors are streaming "The Wheel of Time" > (appropriately, for time-nuts) - varies wildly over a short time. (I will say > that WiFi latency improves dramatically during a power failure in a > residential neighborhood when you have backup power, and your neighbors do > not) > > Imagine NTP running over Starlink, especially when there are multi hop > crosslinks between satellites. At 7 km/s orbital velocity, the range is > changing as much as 21 microseconds/second to a "stationary" observer. Now > consider two satellites in different orbital planes. The dynamics of the > latency get quite complex. > > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
