My Asus RT-AC68U setting to fight buffer bloat ECN

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bsmithline
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Joined: 28 Aug 2009
Posts: 5

PostPosted: Sun May 17, 2015 19:16    Post subject: My Asus RT-AC68U setting to fight buffer bloat ECN Reply with quote

This is how I setup my Asus RT-AC68U to fight buffer bloat

Used: DD-WRT v24-sp2 (03/05/15) std (SVN revision 26446)

Available: ftp://ftp.dd-wrt.com/betas/2015/03-05-2015-r26446/asus-rt-ac68u/asus_rt-ac68u-firmware.trx

One I found at dd-wrt.com v24 PreSP2 [Beta] Build:23940 had problem with port forwards that would cause the RT-AC68U to crash/restart....

Workstation set to use ECN from the guide found at http://en.wikipedia.org/wiki/Explicit_Congestion_Notification.

Before any changes where made on Fontier FIOS 25 MB connection received an "F" on the DSLREPORTS speed test. With Qos set to enable Port:WAN Packet Schedule:HTB Queueing Discipline the best I could do was "C" on the test even with workstations ECN set to on.


http://www.bufferbloat.net/projects/bloat/wiki/Linux_Tips

Enable ECN, SACK, and DSACK

These sysctl settings can be stored in the main /etc/sysctl.conf file, or in a file in the /etc/sysctl.d directory [NOT WITH .DD-WRT v24-sp2 (03/05/15) std (SVN revision 26446) FIRMWARE]

net.ipv4.tcp_ecn=1
net.ipv4.tcp_sack=1
net.ipv4.tcp_dsack=1

Note that there is still some broken ECN CPE (e.g. home router) equipment out there; if you have problems in some environments, please let us know.


TELNET to RT-AC68U login: root then the password you used when you setup dd-wrt on RT-AC68U

Only change need to DD-WRT v24-sp2 (03/05/15) std (SVN revision 26446)

echo 1 >/proc/sys/net/ipv4/tcp_enc

To check values make sure all are 1 [ note

cat /proc/sys/net/ipv4/tcp_enc
cat /proc/sys/net/ipv4/tcp_sack
cat /proc/sys/net/ipv4/tcp_dsack

If not use echo 1 >/proc/sys/net/ipv4/tcp_XXXX for the one you need to change.

Changed value in dd-wrt NAT / QoS tab

Packet Scheduler to HFSC

Test run at http://www.dslreports.com/speedtest HTML 5 now show either an A or A+.
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MDA400
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Joined: 10 Jan 2015
Posts: 62

PostPosted: Mon May 18, 2015 4:32    Post subject: Reply with quote
Actually there is a wiki for the correct QoS settings:
http://www.dd-wrt.com/wiki/index.php/Quality_of_Service

HTB scheduler, FQ_Codel queue discipline, and 80-90% bandwidth limit is the recommended. ECN is fine to have enabled, but alone it doesn't do enough for an entire network's bufferbloat and isn't available in every device (playing a game and downloading a file at the same time/walking and chewing gum).

The dslreports test isnt the best indicator for buffer bloat. You must ping a website like google from command line then fully saturate your connection and observe how big the variation in latency is (jitter).
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