[Bloat] sfqred and RTT testing at 4Mbit

[Dave Taht]

In the little remaining time I have in France I have been testing out
Eric Dumazet's implementation of REDSFQ, against two boxes with
his newer SFQ on them. I need to take time out to do this work
in isolation, but I'm out of time for the next several weeks to do
so.

Baseline numbers to:

* one hop router

64 bytes from 172.30.50.1: icmp_req=2 ttl=64 time=0.245 ms

two hop router
64 bytes from 172.30.47.1: icmp_req=1 ttl=63 time=0.610 ms

During this test I am pinging away with a 10ms
stream, which stays at or below...

172.30.50.1 : [999], 248 bytes, 2.56 ms (2.55 avg, 0% loss)

for 100% of the samples.

(this is my attempt at simulating voip to some extent)

And 10 iperfs going to the closest router do:

[ 12]  0.0-66.3 sec  2.75 MBytes   348 Kbits/sec
[ 13]  0.0-66.3 sec  2.75 MBytes   348 Kbits/sec
[  8]  0.0-66.3 sec  2.75 MBytes   348 Kbits/sec
[ 11]  0.0-66.4 sec  2.75 MBytes   348 Kbits/sec
[  9]  0.0-66.4 sec  2.75 MBytes   348 Kbits/sec
[ 10]  0.0-66.4 sec  2.75 MBytes   348 Kbits/sec
[  6]  0.0-66.4 sec  2.75 MBytes   347 Kbits/sec
[  5]  0.0-67.2 sec  2.88 MBytes   359 Kbits/sec
[  7]  0.0-67.2 sec  2.88 MBytes   359 Kbits/sec
[  4]  0.0-67.2 sec  2.88 MBytes   359 Kbits/sec
[SUM]  0.0-67.2 sec  27.9 MBytes  3.48 Mbits/sec

vs a single latecomer RTT stream, started
after those and ending before them (because
I told it to run for 55 seconds, not 60), to the
further router:

[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-60.7 sec  2.62 MBytes   363 Kbits/sec

You'll note that the iperf tests tend to run longer than 60
seconds for some reason, but the net result is statistically
right in the ballpark.

$TC -s qdisc show dev eth0
qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0
 Sent 130783919 bytes 93092 pkt (dropped 1, overlimits 177024 requeues 0)
 rate 1744bit 2pps backlog 0b 0p requeues 0
qdisc sfq 10: parent 1:1 limit 120p quantum 1514b depth 16 headdrop
divisor 16384
 ewma 6 min 1500b max 18000b probability 0.12 ecn
 prob_mark 0 prob_mark_head 3223 prob_drop 0
 forced_mark 0 forced_mark_head 0 forced_drop 0
 Sent 130783919 bytes 93092 pkt (dropped 1, overlimits 3223 requeues 0)
 rate 1728bit 2pps backlog 0b 0p requeues 0

To set this up:

I am not going to claim this is a correct setting for redsfq, but it
is certainly
the simplest qdisc setup for a shaper I've yet seen. Many of these params
may well be optional...

tc qdisc del dev eth0
tc qdisc add dev eth0 root handle 1: est 1sec 8sec htb default 1
tc class add dev eth0 parent 1: classid 1:1 est 1sec 8sec \
                        htb rate 4Mbit mtu 1500 quantum 4500
qdisc add dev eth0 parent 1:1 handle 10: est 1sec 4sec sfq \
                        limit 120 headdrop flows 64 divisor 16384 \
                        redflowlimit 40000 min 1500 max 18000 \
                        depth 16 probability 0.12 ecn

For a single stream at this setting, I get:

[14]  0.0-60.6 sec  27.5 MBytes  3.81 Mbits/sec

which translates out well to decimal megabits, which keep mentally
messing with me.

3.81*1.05
4.00

the packet captures are lovely, and it's nice to see ecn working.

I also did a 24 hour wireless stress test against both the latest
cerowrt and two laptops
without ever dropping a connection... and similar results.

Now I pack for Britain!

-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
FR Tel: 0638645374
http://www.bufferbloat.net