Re: [time-nuts] wifi with time sync

Hi, On Sat, Jan 14, 2017 at 1:30 AM, walter shawlee 2 wrote: > While probably not tight enough for time nuts use, there is a new WiFi > technology shown at CES that provides time sync between nodes to allow audio > to be simulcast over many locations. the info (in short

Re: [time-nuts] wifi with time sync

Sonos and I guess their competitors do this by dropping WiFi compatibility. They exist on their own network in the same ISM band so I wonder how well they coexist with WiFi. Online reports say poorly under crowded band conditions. On Sun, 15 Jan 2017 09:50:05 -0500, you wrote: >Hi > >The push

Re: [time-nuts] wifi with time sync

Modern systems are very aggressive about DVFS (dynamic voltage and frequency scaling) so it would not surprise me at all. I have run across this problem on the timescale of one second even on 10 year old desktop hardware. On Sun, 15 Jan 2017 09:32:56 -0500, you wrote: >Hi > >I’d be surprised if

Re: [time-nuts] wifi with time sync

Hi Bob, Below are some efforts to reduce buffering in both routers and non router network stacks including wifi. They are focusing on reducing latency - maybe some is relevant for you. https://www.bufferbloat.net/projects/make-wifi-fast/wiki/ https://wiki.openwrt.org/doc/howto/sqm

Re: [time-nuts] wifi with time sync

Hi The push behind this is whole house audio. These guys want to be able to set up WiFi speakers / mic's all through a home and get proper audio imaging in each room. They likely also want to use it to figure out which mic you are talking to using time of arrival. They very much want to do

Re: [time-nuts] wifi with time sync

On 1/15/17 6:27 AM, Bob Camp wrote: Hi Again, this is why the interest in “how the heck did they accomplish it? With the claim of microsecond level performance, they must have run into all these issues. or is it "with these two specific WiFi adapters in this specific environment, we were

Re: [time-nuts] wifi with time sync

Hi I’d be surprised if a laptop running on wall power and doing a variety of low level traffic every second is throttling the chip set. It *is* doing something weird and that certainly is one candidate. I’m not quite as concerned with the *why* the bumps occur (though I am curious). I’m more

Re: [time-nuts] wifi with time sync

Hi Again, this is why the interest in “how the heck did they accomplish it? With the claim of microsecond level performance, they must have run into all these issues. Just a note: any time I want to do anything that matters, I put it on 5 GHz. There are still issues, but not quite as

Re: [time-nuts] wifi with time sync

Bob, I think you are pushing me in this direction, but it was my conclusion before this discussion even began. Most consumer WiFi devices will quiesce the WiFi chipset between major consumer-initiated usages for battery savings, so it's not surprising to see a good amount of random variation in

Re: [time-nuts] wifi with time sync

I haven't read the entire thread, but this may be relevant. If not, you know where to find the delete key. I live in a life care community - one of 450 people in 300 apartments on 3 floors. When I moved in a year ago, I could get Internet from the house cable, and they provided the modem. I

Re: [time-nuts] wifi with time sync

Yes, it will be interesting to see how well wifi rtt/tof does indoors with plenty of multipath. But for sure sub microsecond. On Sat, Jan 14, 2017 at 6:32 PM Bob Camp wrote: > Hi > > > > > > > On Jan 14, 2017, at 5:29 PM, Scott Stobbe > wrote: > > > > >

Re: [time-nuts] wifi with time sync

On 1/14/17 4:25 PM, Bob Camp wrote: Hi Maybe the magic stamping has been hiding in the chips all along. What’s pretty clear is that if it’s there, it’s well hidden …. or totally unstandardized - it might be one of those "we put it in for manufacturing test" features, and everyone does it

Re: [time-nuts] wifi with time sync

Hi Maybe the magic stamping has been hiding in the chips all along. What’s pretty clear is that if it’s there, it’s well hidden …. Bob > On Jan 14, 2017, at 7:04 PM, jimlux wrote: > > On 1/14/17 3:32 PM, Bob Camp wrote: >> Hi >> >> >>> On Jan 14, 2017, at 5:29 PM,

Re: [time-nuts] wifi with time sync

On 1/14/17 3:32 PM, Bob Camp wrote: Hi On Jan 14, 2017, at 5:29 PM, Scott Stobbe wrote: I don't think wifi is ever going to be a real-time system, as it shares the ether with all other ISM devices. That said even 1 ms of variation is still 4 orders of magnitude

Re: [time-nuts] wifi with time sync

Hi > On Jan 14, 2017, at 5:29 PM, Scott Stobbe wrote: > > I don't think wifi is ever going to be a real-time system, as it shares the > ether with all other ISM devices. That said even 1 ms of variation is still > 4 orders of magnitude greater than the actual time of

Re: [time-nuts] wifi with time sync

I don't think wifi is ever going to be a real-time system, as it shares the ether with all other ISM devices. That said even 1 ms of variation is still 4 orders of magnitude greater than the actual time of flight. The precision time aspect will most certainly be done in hardware, even if it's

Re: [time-nuts] wifi with time sync

Hi Here’s what I am seeing: 64 bytes from 192.168.2.2: icmp_seq=3700 ttl=64 time=5.025 ms 64 bytes from 192.168.2.2: icmp_seq=3701 ttl=64 time=4.579 ms 64 bytes from 192.168.2.2: icmp_seq=3702 ttl=64 time=1.511 ms 64 bytes from 192.168.2.2: icmp_seq=3703 ttl=64 time=1.601 ms 64 bytes from

Re: [time-nuts] wifi with time sync

kb...@n1k.org said: > Ok, what I see is that every few hours, I get a “rogue delay” on a single > ping. How would NTP help me spot a single transit with a 250 ms round trip > and identify the time it occured? Keep in mind that NTP is going to > throttle back to a very low level of “chat”

Re: [time-nuts] wifi with time sync

Sorry as this is perhaps a bit off topic but I've tried to make this somewhat time nuts relevant. Over the years I found ping tests have worked quite well (at least on WAN links) to roughly measure network bandwidth. When I used to visit remote sites with WAN links I would often perform

Re: [time-nuts] wifi with time sync

I merely used the ping to demonstrate Wireshark's packet time stamping (though in this case, it seems that the router responds immediately). FWIW, a couple of NTP packets got captured too with a 34 ms round trip. I was actually looking for an ARP request/response in consecutive packets on the

Re: [time-nuts] wifi with time sync

Hi > On Jan 14, 2017, at 1:38 PM, Chris Albertson > wrote: > > On Sat, Jan 14, 2017 at 7:46 AM, Bob Camp wrote: > >> Hi >> >> Ok, what I see is that every few hours, I get a “rogue delay” on a single >> ping. How >> would NTP help me spot a single

Re: [time-nuts] wifi with time sync

Hi The issue with using Wireshark is that it still is looking at a ping. It may tag the event to one more digit, but all of the earlier mentioned issues with pings are still there. Simply put, they aren’t the greatest thing for testing timing. Bob > On Jan 14, 2017, at 1:51 PM, Orin Eman

Re: [time-nuts] wifi with time sync

You could run a network monitor, Wireshark for example... https://wiki.wireshark.org/CaptureSetup/WLAN There are specialized WIFI capture programs, but they tend to be designed to break into networks rather than monitor performance - kismet/kismac. I run them every so often to check for

Re: [time-nuts] wifi with time sync

On Sat, Jan 14, 2017 at 7:46 AM, Bob Camp wrote: > Hi > > Ok, what I see is that every few hours, I get a “rogue delay” on a single > ping. How > would NTP help me spot a single transit with a 250 ms round trip and > identify the > time it occured? Keep in mind that NTP is going

Re: [time-nuts] wifi with time sync

Hi > On Jan 14, 2017, at 12:44 PM, jimlux wrote: > > On 1/14/17 8:35 AM, Bob Camp wrote: >> Hi >> > >> >> I also believe that ping data is one way to come up with an upper bound on >> just how awful WiFi timing can be. If others have a similar single shot >> measure

Re: [time-nuts] wifi with time sync

On 1/14/17 8:35 AM, Bob Camp wrote: Hi I also believe that ping data is one way to come up with an upper bound on just how awful WiFi timing can be. If others have a similar single shot measure of WiFi round trip that can be run on a wide range of devices, I’d certainly be just as

Re: [time-nuts] wifi with time sync

Hi We have a double issue here: 1) It’s a problem because “not enough information was given" 2) It’s a problem because “we are talking about it to much” Sorry, but there is absolutely no way at all both of those criteria can be met by me. I do believe that WiFi time protocols are an on

Re: [time-nuts] wifi with time sync

On 1/14/17 7:53 AM, John Hawkinson wrote: I tried to engage with you off-list and give you some pointers on this, but that does not seem to be working. Consumer wifi driver problems are manifestly inappropriate for this list, and trying to do both at once leads to gross confusion :( I know this

Re: [time-nuts] wifi with time sync

On 1/14/17 7:46 AM, Bob Camp wrote: Hi Ok, what I see is that every few hours, I get a “rogue delay” on a single ping. How would NTP help me spot a single transit with a 250 ms round trip and identify the time it occured? Keep in mind that NTP is going to throttle back to a very low level of

Re: [time-nuts] wifi with time sync

This has nothing to do with time-nuts, can it stop please? [ I don't know what forum to send you to for "weird wifi problems"; there is probably no good one, because it is a very common consumer problem :( ] NTP was mentioned because you (Bob Camp) had not defined the problem very well, and

Re: [time-nuts] wifi with time sync

Hi This is very much a one laptop to one router issue. The other couple dozen laptops and tablets do not see an issue. The whole thing started when a series of firmware updates rolled through a few weeks ago. The laptop is *maybe* 12 feet from the router. It’s running at 5 GHz so microwaves

Re: [time-nuts] wifi with time sync

Hi Ok, what I see is that every few hours, I get a “rogue delay” on a single ping. How would NTP help me spot a single transit with a 250 ms round trip and identify the time it occured? Keep in mind that NTP is going to throttle back to a very low level of “chat” quite quickly….. While this

Re: [time-nuts] wifi with time sync

If there is a modern microwave oven with a switching power supply, or a cordless telephone around, you might want to look there. The old linear supply ovens were easy to deal with because they presented a strong CW signal that drifted around as voltage, load, and temperature changed. The

Re: [time-nuts] wifi with time sync

On Fri, Jan 13, 2017 at 1:11 PM, Bob Camp wrote: > Hi > > Ok. so I bring up NTP on the laptop against a server on the other side of > the country and install > NTP on the laptop. I get all of the jitter and offset of my cable modem > plus the network > issues between here and who

Re: [time-nuts] wifi with time sync

On Fri, Jan 13, 2017 at 8:45 PM, Chris Albertson wrote: > Short answer: See man page for ntpq > > Longer... > > First run NTP then after some time (15 minute to an hour) at the command > line time type "ntpq -p" > > "ntpq" will query NTP for timing statistics. It will

Re: [time-nuts] wifi with time sync

On Fri, Jan 13, 2017 at 3:35 PM, Bob Camp wrote: > Hi > > What standard protocol would you recommend I run from the command line on > my computer > to get a quick estimate of the timing lag and variablilty on my > particular WiFi connection? If I wanted to do this I would use

Re: [time-nuts] wifi with time sync

> What standard protocol would you recommend I run from the command line on my > computer to get a quick estimate of the timing lag and variablilty on my > particular WiFi connection? I'd use ping. But you said "quick estimate". My wifi is crappy enough that its noise swamps everything

Re: [time-nuts] wifi with time sync

On 1/13/17 2:19 PM, Chris Caudle wrote: On Fri, January 13, 2017 3:17 pm, Bob Camp wrote: It just so happens that I'm trying to track down an issue with my WiFi as I type this. This is getting off topic for time-nuts very quickly, well, wireless distribution of accurate time is, I think, on

Re: [time-nuts] wifi with time sync

On Fri, January 13, 2017 3:17 pm, Bob Camp wrote: > It just so happens that I'm trying to track down an issue with my WiFi > as I type this. This is getting off topic for time-nuts very quickly, but use bufferbloat and "make wifi fast" as search phrases. The guy who did a lot of the work on

Re: [time-nuts] wifi with time sync

It’s a little more complicated than that. A switch’s main cpu is like a host with rx coalesce set to 100. And there are a surprising number of things that trigger the main cpu beyond management functions. Multicast is a good example. The amount of load on the main cpu can be quite variable, and

Re: [time-nuts] wifi with time sync

Hi It just so happens that I’m trying to track down an issue with my WiFi as I type this. My *guess* is that there is a dropout going on. The only easy way I can see to get a round trip time with a high data rate is to run ping. It’s the only tool that gives me something that is fast enough to

Re: [time-nuts] wifi with time sync

To add to this I'd be curious in knowing about easy PC based ways to measure network latencies / delays with microsecond accuracy vs millisecond accuracy. The tools I used to use at work were generally designed for use on networks where millisecond resolution measurements made sense as a

Re: [time-nuts] wifi with time sync

Bob Camp wrote on Fri, 13 Jan 2017 at 15:35:19 -0500 in : > What standard protocol would you recommend I run from the command > line on my computer to get a quick estimate of the timing lag and > variablilty on my particular WiFi

Re: [time-nuts] wifi with time sync

Hi Ok. so I bring up NTP on the laptop against a server on the other side of the country and install NTP on the laptop. I get all of the jitter and offset of my cable modem plus the network issues between here and who know where. If I want to know the specific delay issues just on the WiFi

Re: [time-nuts] wifi with time sync

Hi That *assumes* that NTP is installed on the laptop. Bob > On Jan 13, 2017, at 3:45 PM, Chris Albertson > wrote: > > Short answer: See man page for ntpq > > Longer... > > First run NTP then after some time (15 minute to an hour) at the command > line time type

Re: [time-nuts] wifi with time sync

Short answer: See man page for ntpq Longer... First run NTP then after some time (15 minute to an hour) at the command line time type "ntpq -p" "ntpq" will query NTP for timing statistics. It will report the average delay between the local computer and the set of reference clocks (other

Re: [time-nuts] wifi with time sync

Hi What standard protocol would you recommend I run from the command line on my computer to get a quick estimate of the timing lag and variablilty on my particular WiFi connection? Bob > On Jan 13, 2017, at 3:25 PM, John Hawkinson wrote: > > Can we please stop talking about

Re: [time-nuts] wifi with time sync

Even with the long and variable ping time, time sync can work. The reason it can work is that time is not re-sync'd in one "ping" but time sync is an on-going process that occurs over a period as long as hours. Think about adjusting the rate of a clock by hand. The computer (NTP) can (and does)

Re: [time-nuts] wifi with time sync

Can we please stop talking about pings? Bob Camp wrote on Fri, 13 Jan 2017 at 15:12:38 -0500 in : > I’m sure you are right about the response time. Right now the > variation is running almost 3 ms at one sigma on a ping so there is >

Re: [time-nuts] wifi with time sync

Hi I’m sure you are right about the response time. Right now the variation is running almost 3 ms at one sigma on a ping so there is a lot to do simply to get the accuracy anywhere near 1 us. Bob > On Jan 13, 2017, at 2:35 PM, Chris Caudle wrote: > > On Fri, January

Re: [time-nuts] wifi with time sync

On Fri, January 13, 2017 11:40 am, Bob Camp wrote: > The ping response is anywhere from 2 ms out to 400 ms. Most of > the time it's in the 3 to 9 ms range. Simply taking that > down to < 1 us would be a really big deal. I doubt that the response time will get that low, rather the time sync will

Re: [time-nuts] wifi with time sync

Hi I probably should have added that I already know that the switch will do sub 1 ms LAN pings all day long with the near zero load that it’s running. Sorry about that. Now, there certainly are OS level things on my laptop that will muck up pings. Unfortunately they also get into a number of

Re: [time-nuts] wifi with time sync

> On Jan 13, 2017, at 09:40, Bob Camp wrote: > > Just for reference, I happen to be running a ping over my local WiFi to one > of the switches > on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of > the time it’s > in the 3 to 9 ms range. Simply taking

Re: [time-nuts] wifi with time sync

I saw this article too -- is anyone aware of something with more technical details? For example, where in the protocol stack does it work? Is it specific to 802.11 or general purpose ethernet? Speaking as someone who has a primary hobby of the development of super low cost time sync algorithms

Re: [time-nuts] wifi with time sync

On Fri, January 13, 2017 10:59 am, Bob Camp wrote: > 1588 is a "less than a microsecond" sort > of approach that does indeed get down to nanosecond > sort of levels. This could be similar. There was talk of adding a wireless profile into 1588 either as an addendum or as part of PTPv3. I suspect

Re: [time-nuts] wifi with time sync

Hi Just for reference, I happen to be running a ping over my local WiFi to one of the switches on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of the time it’s in the 3 to 9 ms range. Simply taking that down to < 1 us would be a really big deal. Bob > On Jan 13,

Re: [time-nuts] wifi with time sync

Hi A lot depends on how much “less than a microsecond” the chip sets really deliver in the real world. If they get down into the sub 100 ns range (which they might), it’s a very useful thing for relaying GPS data from a roof antenna down to an NTP server in the basement. 1588 is a “less than a

Re: [time-nuts] wifi with time sync

they were really short on hard details about this new technology. the *WiFi alliance* website only shows this off-site article link I found under NEWS:

[time-nuts] wifi with time sync

While probably not tight enough for time nuts use, there is a new WiFi technology shown at CES that provides time sync between nodes to allow audio to be simulcast over many locations. the info (in short form) is here for those interested: