[tor-relays] Measuring the Accuracy of Tor Relays' Advertised Bandwidths

[Rob Jansen]

> On Jul 26, 2019, at 10:35 AM, Roger Dingledine <arma at torproject.org> wrote:
> 
> On Fri, Jul 26, 2019 at 10:18:24AM -0400, Rob Jansen wrote:
>> I am planning on performing an experiment on the Tor network to try to gauge the accuracy of the advertised bandwidths that relays report in their server descriptors. Briefly, the experiment involves running a speed test on every relay for a short time (about 20 seconds).
> 
> Thanks Rob!
> 
> For context, I asked Rob to do this experiment, because we know that
> the current bandwidth authority design is mis-measuring relays, but we
> don't know how wrong things are. Giving every relay a short burst of
> load should give us some insight into how much traffic that relay can
> handle, which will in turn tell us how much room for improvement there
> is in our bandwidth estimation.
> 
> And as a bonus, for this one time, fast relays should actually be
> consistently seen as fast, and the Tor network should be better balanced
> and the user experience should be better. If we like how it works,
> our follow-up task will be to change things so we get this result all
> the time. :)

Over the last 2 days I tested my speedtest on 4 test relays and verified that it does in fact increase relays' advertised bandwidth on Tor metrics.

Today, I started running the speedtest on all relays in the network. So far, I have finished about 100 relays (and counting). I expect that the advertised bandwidths reported by metrics will increase over the next few days. For this to happen, the bandwidth histories observed by a relay during my speedtest are first committed to the bandwidth history table (within 24 hours), and then reported in the server descriptors (within 18-36 hours, depending on when the bandwidth history commit happens).

Peace, love, and positivity,
Rob