[Ecn-sane] osx ecn

[Dave Taht]

An interesing piece of this is how often the syn attempt is failing.

             2192 times graceful fallback to Non-ECN connection

                2053 times lost ECN negotiating SYN, followed by retransmission

??

Now, there are plenty of reasons to lose syns (most firewalls rate limit these),
besides the ecn flag.

In my case during this boot cycle I've been engaged in a fun
experiment - and one day perhaps a paper - Going to various coffee
shops in the area and running the attached script. The results thus
far are universally dismal,
except for google starbucks which is excellent - but the packet
captures seem to indicate something in addition to
or other than than fq_codel in use (dpi maybe? aruba is the next hop)
AND it did not negotiate ecn when I last tried.

Wifi spread initially through the coffee shop phenomenon, and I've
"lept over the counter" a couple times
to help configure the to-the-isp qos system when I found an owner with
clue, which helps a lot. When I showed 'em the before/after two bought
me lunch (and I can highly recommend https://www.cemitas1.com/ in
davenport for food, music, view & wifi) if that's a motivator for more
folk here "to get out more", please do so. Table service is a nice
thing to have when in deep hack mode and socializing more helps too. :

daves-Air-6:los_gatos_starbucks d$ more testit.sh

#!/bin/sh

T="Los_Gatos_Starbucks"
F="flent -x -H flent-fremont.bufferbloat.net -t $T" # pick a closer
flent server and on linux use --socket-stats
$F --te=download_streams=4 tcp_ndown
$F --te=upload_streams=4 tcp_nup
$F --te=upload_streams=4 tcp_2up_square
$F rrul
$F rrul_be

On Tue, Aug 27, 2019 at 12:02 AM Mikael Abrahamsson <swmike at swm.pp.se> wrote:
>
> On Tue, 27 Aug 2019, Michael Welzl wrote:
>
> > run it as root - strange, yes, but then the output is very different.
>
> Thanks, indeed.
>
> $ sudo netstat -sp tcp | egrep 'CE|EC'
>         11097 client connections attempted to negotiate ECN
>                 4864 client connections successfully negotiated ECN
>                 3800 times graceful fallback to Non-ECN connection
>                 467 times lost ECN negotiating SYN, followed by retransmission
>                 52 server connections attempted to negotiate ECN
>                 52 server connections successfully negotiated ECN
>                 0 time lost ECN negotiating SYN-ACK, followed by retransmission
>                 427 times received congestion experienced (CE) notification
>                 0 time CWR was sent in response to ECE
>                 6111 times sent ECE notification
>                 15 connections received CE atleast once
>                 0 connection received ECE atleast once
>                 267 connections using ECN have seen packet loss but no CE
>                 1 connection using ECN have seen packet loss and CE
>                 14 connections using ECN received CE but no packet loss
>                 14 connections fell back to non-ECN due to SYN-loss
>                 1 connection fell back to non-ECN due to reordering
>                 0 connection fell back to non-ECN due to excessive CE-markings
>
>
> --
> Mikael Abrahamsson    email: swmike at swm.pp.se



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740