From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
To: Kathleen Nichols <nichols@pollere.com>, bloat@lists.bufferbloat.net
Subject: Re: [Bloat] Bufferbloat test measurements
Date: Sat, 27 Aug 2016 20:39:39 +0100 [thread overview]
Message-ID: <1625876f-57ac-06c7-8202-e24081d9c491@gmail.com> (raw)
In-Reply-To: <1091de30-017f-e6ee-a440-cd8425be0e1a@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2383 bytes --]
On 27/08/16 20:18, Alan Jenkins wrote:
> On 27/08/16 18:37, Kathleen Nichols wrote:
> So, I ran the test while I was also streaming a
>> Netflix video. Under the column "RTT/jitter Avg" the test lists
>> values that
>> range from 654 to 702 with +/- 5.2 to 20.8 ms (for the four servers). I
>> couldn't
>> figure out what that means.
>
> My assumption is the RTT is just read out from the TCP socket, i.e.
> it's one of the kernel statistics.
>
> http://stackoverflow.com/questions/16231600/fetching-the-tcp-rtt-in-linux/16232250#16232250
>
>
> Looking in `ss.c` as suggested, the second figure shown by `ss` is
> `rttvar`. And that's the kernel's measure of RTT variation. If my
> assumption is right, that would tell us where the "jitter" figure
> comes from as well.
Sadly I don't think anyone's volunteered to restore the GMane web
interface yet. NNTP is still searchable though.
I'm not sure whether the author is saying they _are_ showing kernel
stats, or whether they ended up having to do their own RTT calculation.
(This is the Justin who runs dslreports.com).
-------- Forwarded Message --------
Subject: Re: delay-under-load really helps diagnose real world problems
Date: Sat, 25 Apr 2015 12:23:28 +1000
From: jb <justin-rsQtcOny2EM@public.gmane.org>
To: Matthew Ford <ford-pYXoxzOOsG8@public.gmane.org>, bloat
<bloat-JXvr2/1DY2fm6VMwtOF2vx4hnT+Y9+D1@public.gmane.org>
Newsgroups: gmane.network.routing.bufferbloat
References:
<AE7F97DB5FEE054088D82E836BD15BE9319C249E@xmb-aln-x05.cisco.com>
<22118EDD-F497-46F3-AC6A-A75C389DFBAB@isoc.org>
I have made the following changes a few hours ago:
Bloat latency stats run on every connection now except GPRS and 3G
if you don't seem them during the test (mobile), they should be there
afterwards.
Download phase waits for quiescent latency measurements, defined by
less than 2x the lowest ping seen, or it simply gives up waiting and
continues.
The flow stats table has combined stats per server, so the megabit per
stream are
summed and the other measurements are averaged. I'm not entirely trusting
of the RTT and RTT Variance numbers from Linux, they come from the TCP_INFO
structure but are probably heavily biased to the end of the connection
rather
than the entire connection. However the re-transmits are definitely ok and
the
congestion window packet count looks about right too.
that's it..
[-- Attachment #2: Type: text/html, Size: 3993 bytes --]
next prev parent reply other threads:[~2016-08-27 19:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-27 11:46 [Bloat] Bufferbloat test measurements (was: Open Source Speed Test) Rich Brown
2016-08-27 15:19 ` Kathleen Nichols
2016-08-27 16:03 ` [Bloat] Bufferbloat test measurements Alan Jenkins
2016-08-27 17:37 ` Kathleen Nichols
2016-08-27 19:18 ` Alan Jenkins
2016-08-27 19:39 ` Alan Jenkins [this message]
2016-08-27 23:39 ` jb
2016-08-28 0:14 ` Kathleen Nichols
2016-08-28 2:23 ` jb
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=1625876f-57ac-06c7-8202-e24081d9c491@gmail.com \
--to=alan.christopher.jenkins@gmail.com \
--cc=bloat@lists.bufferbloat.net \
--cc=nichols@pollere.com \
/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