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

[Rob Jansen]

> On Jul 31, 2019, at 7:34 PM, teor <teor at riseup.net> wrote:
> 
> Hi Rob,
> 

Hey there!

> Can you define "goodput"?

Application-level throughput, i.e., bytes transferred in packet payloads but not counting packet headers or retransmissions. In our case I mean the number of bytes that Tor reports in the BW controller event.

> How is it different to the bandwidth reported by a standard speed test?

I believe that iperf also reports goodput as defined above.

> How is it different to the bandwidth measured by sbws?

I am not an expert on sbws, but I believe it also measures goodput.

> Where is your server?

West coast US.

> How do you expect the location of your server to affect your results?

I expect that the packet loss that occurs between my measurement machine and the target may limit the goodput I am able to achieve, and packet loss tends to occur more frequently on links with higher latency. I plan to use multiple sockets (as standard speed testing tools like iperf do) and multiple circuits to try to mitigate the effects.

Note that this is meant to be a fairly simple experiment, not a complete measurement system. Of course I won't be able to measure more than the bandwidth capacity of my measurement machine, but many relays already carry significant load so I'll just be giving them a boost.

Peace, love, and positivity,
Rob