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

David Fifield david at bamsoftware.com
Tue Sep 16 04:07:58 UTC 2014

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.

> 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.

David Fifield

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