[tor-relays] Consensus Weight calculation

Vort vvort at yandex.ru
Tue Jun 13 16:01:22 UTC 2017


> We know of relays that have improved their bandwidth measurements by
> changing their keys (this resets the measurements).

1. It is not possible to change keys for relays which you don't control.
2. It is better to have such algorithms, which can't stuck.


> But most relays get low weights because:
> * they can not get enough CPU or RAM,
> * they can not keep enough connections open,

This is not a case for relays with 1 KiB/s load.

> * they go up and down a lot,

My examples was for stable relays.

> * they change IP address a lot, or

ExoneraTor is lagging, but 3 of 4 example relays was using
  the same addresses month ago.

> * they do not get good bandwidth over time,
> * they do not get good bandwidth to the rest of the tor network,
> * they have high latency to the rest of the tor network,

This can be measured.
For example, BD4354E76929C90B7004FF149A3C52189A3B4634 is capable of
  serving 1 MiB/s (was made a circuit through it this morning):

r Hedgehog vUNU52kpyQtwBP8UmjxSGJo7RjQ BG894JEWmT0pcLmWTabGYlWT5Iw 2017-06-13 06:08:30 212.26.140.81 443 0
...
w Bandwidth=1024 Measured=5

> * some other reasons that make them less useful to clients.

Looks like clients have no influence on BwAuth's decisions.


> But this isn't enough information to work out what the problem is.
> Maybe there is a problem with the relay, not the measurements.
> We just can't tell.

What additional information can help?


> Maybe the relay has low CPU, international bandwidth, or connection
> limits. We just don't know.

If it can retranslate a lot of traffic, then it have no such problems.


> We would need to talk to the operator to find out.

I would not raised this question if I wasn't such an operator.


> These measurements are updated over time.
> Please check again after a few weeks.

They already shows that relay is more capable than it is rated.


> I think this spike means:

> "You think your provider is giving you 100 Mbps, but they are
> actually giving you much less. Talk to them about it."

> Usually this is because the provider only tries to give everyone
> 100Mbps, or they limit everyone and don't tell them, or they don't
> pay enough to get good international bandwidth.

Exact number does not matter.
The problem is that weight histogram have no equivalent spike.


Here is another histogram.
https://s8.hostingkartinok.com/uploads/images/2017/06/749e7e3be806c22f3dd5c0e9586304ab.png
(x, y and colors are the same)
Just filtered relays so theirs Advertised Bandwidth is in range 1100000..1350000.
I wouldn't say this values are "proportional" enough.


-- Vort



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