[tor-dev] Proposal XXX: FlashFlow: A Secure Speed Test for Tor (Parent Proposal)

[Mike Perry]

On 4/23/20 1:48 PM, Matt Traudt wrote:

> 5.4 Other Changes/Investigations/Ideas
>
> - How can FlashFlow data be used in a way that doesn't lead to poor
>   load balancing given the following items that lead to non-uniform
>   client behavior:
>     - Guards that high-traffic HSs choose (for 3 months at a time)
>     - Guard vs middle flag allocation issues
>     - New Guard nodes (Guardfraction)
>     - Exit policies other than default/all
>     - Directory activity
>     - Total onion service activity
>     - Super long-lived circuits
> - What is the explanation for dennis.jackson's scary graphs in this [2]
>   ticket?  Was it because of the speed test? Why? Will FlashFlow produce
>   the same behavior?

It will also be wise to provide a way for relays to signify that they
are on the same machine. I bet concurrent machine deployments are one of
the top contributors to the long tail of bad perf we saw caused by the
Flashflow experiment[2]. If flashflow measures each such relay as having
the full link capacity instead of a shared fraction, this is obviously
going to result in overload on those relays, leading to a long tail of
bad perf when they are chosen and are also overloaded. It is unlikely
that we can deploy a FlashFlow that has this long tail perf problem
without fixing this and related balancing issues (though hopefully most
will be smoothed over by sbws).

This is a little tricky, because we might not want rogue relays joining
each others "machines" (similar to the Family problem), but for testing
something as simple as how MyFamily works would be great. Ideally,
though, relays would ask or detect that they are concurrently running in
nearby IP space and either warn the operator to set the flag, or set it
automatically.

We actually have this work included in a future performance funding
proposal, but the timeline on that getting approved (or even rejected)
is so far out that we should figure out a way to do this before that,
especially if Flashflow development is going to begin soon.

> [2] Mike Perry: Graph onionperf and consensus information from Rob's
>     experiments https://trac.torproject.org/projects/tor/ticket/33076


-- 
Mike Perry