[Cerowrt-devel] smoketest BQL-40 is out

Sebastian Moeller moeller0 at gmx.de
Thu Feb 23 01:21:27 EST 2012

Hi Dave,

I finally got around to update from rc6 to bql-40, to try the ATM shaping. The update was a breeze, great work!
	I am sad to report that for my ATM link AQM does not work for me as well as QoS does. My measurement consists out of using ping to get the RTT to the first ISP hop (as taken from trace route) while concurrently saturating the up link with a dropbox upload (which I usually give that a headstart of 10 seconds to go into bandwidth ceiling): AQM gives the same bad avg RTT of 1.2 seconds as no shaping at all does, while QoS gives me an avg RTT of around 24ms (best case RTT is around 13ms on my link, so the link stays pretty useable).
	I tried to apply the same changes to /usr/lib/aqm/generate.sh and /usr/lib/qos/generate.sh to make the them better understand the peculiarities of my ATM adsl1 connection, but it seems I did something wrong for the AQM script since my change does not have any effect there… (both modified files attached). I usually only  shape up- and down-stream to 97% of the line rate, which works ok with QoS. (And all my tests have been done, very unscientifically, using my mac laptop over the 5GHz wireless band of the router… )

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	While this is not too helpful, it might give some hints for bql-42, as from the roadmap I take it you will tackle the dsl issue there. I am just about to move and switch from DSL to cable internet, so unfortunately this might be my last test…

(BTW, I have been playing with the -s option of ping to change the payload size and for my measly 3008kbps down, 512kbps up connection I can actually see the 48 byte ATM package boundaries in avg RTTs (-c 100), for each new ATM package I roughly get 1ms added to the RTT (as expected when doing the math the my line rate). So I think it should be possible to figure out whether a link uses ATM as carrier or not (IIRC newer ADSL systems like AT&T's verse HSI use ADSL2 over PTM-TC instead of ATM so touch connections still have per package overhead to account for but lack the weird ATM repack issues). 
	I also have a hunch that using this method it should be possible to deduct a link's overhead (as taken understood by tc's step option) from a properly prepared ping sweep. In other words my hypothesis is that it should be possible to run a script on a non-shaped idle link and figure out the optimal parameters for stab. But I digress… (And alas, in two days my DSL connection will be gone and I can not even test my hypothesis in any meaningful way until then...))


On Feb 14, 2012, at 11:53 AM, Dave Taht wrote:

> http://huchra.bufferbloat.net/~cero1/bql-smoketests/bql-40/
> changes in this release:
> kernel 3.3-rc3
> bind 9.9rc2
> ntpd + dnssec removed (too buggy)
> snmpd installed by default
> fprobe installed by default
> avahi installed by default
> sort of better working 'aqm' shaper installed
> ** when configured uses hfsc + sfqred
> ** still has trouble with ipv6, diffserv, and tcp elephants
> ** no adsl overhead support
> I will be travelling later this week. What I'm mostly
> working on right now is better ipv6 support.
> -- 
> Dave Täht
> SKYPE: davetaht
> US Tel: 1-239-829-5608
> FR Tel: 0638645374
> http://www.bufferbloat.net
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel at lists.bufferbloat.net
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