From: Neil Davies <neil.davies@pnsol.com>
To: Hal Murray <hmurray@megapathdsl.net>
Cc: bloat@lists.bufferbloat.net
Subject: Re: [Bloat] Steam In Home Streaming on ath9k wifi
Date: Wed, 22 Nov 2017 10:31:36 +0000 [thread overview]
Message-ID: <1CE2F13E-A918-4EC3-AAEF-3F92DA51C6E3@pnsol.com> (raw)
In-Reply-To: <20171121190826.5B80540605C@ip-64-139-1-69.sjc.megapath.net>
[-- Attachment #1: Type: text/plain, Size: 2718 bytes --]
Hal
We use this approach to automatically manage measurements.
There are a few more issues - the relative drift between the two clocks can be
as high as 200ppm, though typically 50-75ppm is what we observe, but this drift
is monotonic.
Also NTP can make changes at one (or both) ends - they show up as distinct
direction changes in the drift.
This gives a limit (or a measurement error function you have to work within).
Neil
> On 21 Nov 2017, at 19:08, Hal Murray <hmurray@megapathdsl.net> wrote:
>
>> Right, no idea how Windows drivers behave. But odds are that the bottleneck
>> is at the client, since that often has worse antennas than the AP. If you're
>> in a position to take packet captures at both clients and AP you may be able
>> to figure it out; may require tightly synchronised clocks to do properly,
>> though.
>
> It should be reasonable to synchronize the clocks at both ends well enough.
>
> If that doesn't work and/or is inconvient, you could post process one trace
> to adjust the time stamps. The idea is to scan both traces in parallel to
> find the minimum transit times in each direction, then adjust the time stamps
> on one end to allocate half the total time to each direction. It would
> obviously be handy to have a few pings during a period of low traffic for
> calibration.
>
> -------
>
> There are two dimensions to clocks. One is the current time. The other is
> the frequency. If the frequency is off, the clock will drift. (ntpd's drift
> correction is usually stored in someplace like /var/lib/ntp/ntp.drift)
>
> Unless you are interested in long runs, the clock will not drift far enough
> to be a serious problem, so all you have to do is get the time right before
> starting a run.
>
> You might want to kill ntpd on the wifi end so it doesn't get confused and yank the clock around.
>
>
> --
> These are my opinions. I hate spam.
>
>
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat
>
>
> --
> BEGIN-ANTISPAM-VOTING-LINKS
> ------------------------------------------------------
>
> Teach CanIt if this mail (ID 03UAH8AV8) is spam:
> Spam: https://portal.roaringpenguin.co.uk/canit/b.php?c=s&i=03UAH8AV8&m=09f8fdc3b5f4&rlm=pnsol-com&t=20171121
> Not spam: https://portal.roaringpenguin.co.uk/canit/b.php?c=n&i=03UAH8AV8&m=09f8fdc3b5f4&rlm=pnsol-com&t=20171121
> Forget vote: https://portal.roaringpenguin.co.uk/canit/b.php?c=f&i=03UAH8AV8&m=09f8fdc3b5f4&rlm=pnsol-com&t=20171121
> ------------------------------------------------------
> END-ANTISPAM-VOTING-LINKS
>
[-- Attachment #2: Message signed with OpenPGP --]
[-- Type: application/pgp-signature, Size: 801 bytes --]
next prev parent reply other threads:[~2017-11-22 10:31 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-21 19:08 Hal Murray
2017-11-22 10:31 ` Neil Davies [this message]
2017-11-23 17:48 ` Caleb Cushing
2017-11-24 9:20 ` Hal Murray
2017-11-24 9:34 ` Neil Davies
2017-11-26 7:25 ` Caleb Cushing
2017-11-26 7:29 ` Caleb Cushing
2017-11-26 7:55 ` Jan Ceuleers
2017-11-26 10:05 ` Jonathan Morton
2017-11-26 10:53 ` Jan Ceuleers
2017-11-26 10:55 ` Jonathan Morton
2017-11-26 11:54 ` Steinar H. Gunderson
2017-11-26 13:03 ` Jan Ceuleers
2017-11-26 13:05 ` Jan Ceuleers
2017-11-26 13:13 ` Steinar H. Gunderson
2017-11-26 17:53 ` Dave Taht
2017-11-26 18:43 ` Jan Ceuleers
2017-11-26 23:11 ` Dave Taht
2017-12-04 7:24 ` Caleb Cushing
-- strict thread matches above, loose matches on Subject: below --
2017-11-18 22:14 Caleb Cushing
2017-11-19 16:28 ` Toke Høiland-Jørgensen
2017-11-19 21:18 ` Caleb Cushing
2017-11-19 21:27 ` Toke Høiland-Jørgensen
2017-11-19 22:03 ` Caleb Cushing
2017-11-19 22:13 ` Dave Taht
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://lists.bufferbloat.net/postorius/lists/bloat.lists.bufferbloat.net/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1CE2F13E-A918-4EC3-AAEF-3F92DA51C6E3@pnsol.com \
--to=neil.davies@pnsol.com \
--cc=bloat@lists.bufferbloat.net \
--cc=hmurray@megapathdsl.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox