[Netalyzr] upstream buffering test

Jim Gettys jg at freedesktop.org
Sun Mar 4 17:25:59 PST 2012

On 03/04/2012 07:34 PM, Vern Paxson wrote:
> [user Brian dropped from thread for now]
>> Can it not be made to more accurately reflect the actual situation then?
>> ....
>> Ultimately though netalyzer is making people thing they have a
>> bufferbloat problem when they don't, if I'm understanding all of this
>> correctly.
>> I just wonder if the test cannot be made to better reflect the
>> boatedness of the buffer in question so that people are not chasing ghosts.
> Well, he asks a good question.  In particular, if AQM actually is deployed
> a non-trivial proportion of the time, then it really behooves us to try
> to detect that rather than playing into Jim Gettys' pet gripe.

I've never seen netalyzr give me false positives; false negatives, yes,
but not false positives.

However, I'd sure like a test to tell if the ISP is doing AQM or not:
Van doesn't trust the one paper I've seen on the topic (Dischinger, et.
al, IIRC).  And at some point, we sure would like home routers running
an AQM too (Dave Taht has a hack together using RED at the moment, but
CoDel is *much* more interesting...)

I do want to understand better what OpenWrt is actually doing when it's
QOS scripts are invoked.  But I've had a cold this week, and haven't
gone and looked yet.  I know Dave has done major surgery to them in his
recent CeroWrt work.
                        - Jim

> What about doing trying a second flow (ideally, TCP, though that's messy
> to measure) concurrent with the test to see if it's somehow unaffected?
> I'm not sure whether that would fit with his particular setup (depends on
> the nature of the QoS), but would be interesting to try, and he certainly
> sounds willing to test it for us.
> 		Vern
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