[tor-dev] Why the seeming correlation between flash proxy and meek on metrics graphs?

Karsten Loesing karsten at torproject.org
Tue Sep 16 04:21:04 UTC 2014

On 16/09/14 06:07, David Fifield wrote:
> On Tue, Sep 16, 2014 at 05:43:45AM +0200, Karsten Loesing wrote:
>> On 16/09/14 03:36, David Fifield wrote:
>>> In comparing the user graphs of pluggable transports, I found that there
>>> seems to be a correlation between the graphs of flashproxy and meek.
>>> [...]
>>> To figure this out I'm thinking of i) counting bytes transferred on the
>>> flashproxy and meek external ports, or ii) moving one to a different
>>> bridge (or different tor instance), to see if the effect remains. Do you
>>> have any other ideas?
>> Hi David,
>> here's what I think might cause this: we're counting consensuses
>> downloaded from a bridge via any supported transport, and then we're
>> attributing those downloads to specific transports based on what
>> fraction of IPs connected per transport.
> I see! Thank you. I imagine it would make a big difference in this case,
> because flash proxy and meek are polar opposites: flash proxy gets
> connections from tons of random IPs (often different IPs for the same
> client), and meek is always getting connections from the same CDN edge
> servers (the same IP for many different clients). If I understand it
> right, we are over-counting flash proxy and over-counting meek.

Under-counting meek, but yes.

>> What we should do instead is count consensus downloads by transport.
>> There's a ticket for this, but nobody is currently working on it:
>> https://trac.torproject.org/projects/tor/ticket/8786
>> Your idea ii) should fix this.
>> Of course, you'd be in a good position to test a patch for #8786.  Would
>> you want to hack on that?
> We'll see :) For the time being I'll try isolating the transports and
> see what effect it has.

Please keep us posted how that works out.

All the best,

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