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

[teor]

Hi,

> On 24 Aug 2019, at 19:38, Toralf Förster <toralf.foerster at gmx.de> wrote:
> 
>> On 8/19/19 4:56 AM, teor wrote:
>> Yes, changing other relays' bandwidths can affect the Guard flag, because
>> Guard is given to the fastest, most stable relays.
> 
> I'm not convinced that this is the culprit for the mentioned relay [1].
> 
> I found another relay [2] where at least 4 of the 9 authorities doesn't set the "Running" flag, which is needed for "Guard", right?
> That relay has a reasonable bw value to (23,000 , FWIW the value for [1] is about 90,000).
> 
> So now I do wonder why the Running flag is lost after a year.

An authority assigns the Running flag to a relay when it can reach that relay
on its IPv4 ORPort. If the authority is configured to do IPv6 reachability checks,
then it also checks the IPv6 ORPort (if there is one).

> [1]    https://consensus-health.torproject.org/consensus-health-2019-08-24-07-00.html#509EAB4C5D10C9A9A24B4EA0CE402C047A2D64E6

At the moment, 4/9 authorities can't reach this relay. Maybe its provider is
dropping traffic from some routes, or maybe it is overloaded.

> [3]    https://consensus-health.torproject.org/consensus-health-2019-08-24-08-00.html#0CDCFB0B6E1500E57BDD7F240543EBAEF81C11CA

At the moment, 6/9 authorities can't reach this relay. Same possibilities.

T