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Re: [tor-relays] Consensus Weight calculation
> Thanks for writing to us.
Thanks for the answers.
> This is a question that gets asked a lot:
> "Many people set up new fast relays and then wonder why their bandwidth
> is not fully loaded instantly…"
> https://blog.torproject.org/blog/lifecycle-of-a-new-relay
Maybe this is correct in many cases.
But definitely not in all of them.
For example, this line:
"once the bwauths have measured you and the directory authorities lift
the 20KB cap, you'll attract more and more traffic"
Events can go other way: bwauths will assign lower weight, and relay
will be getting less and less traffic.
> It can take a week or two for the bandwidth authorities to measure a
> relay.
Relay, which hit the problem, can be in underpowered state for months.
> I'm not sure if this is a problem. And I'm not sure how many relays it
> impacts.
Hundreds, I guess.
Here is some examples:
https://atlas.torproject.org/#details/9FC2673BB2704C2AAB851F8334938565DF1D0819
Now used bandwidth: 1 KiB/s
Advertised Bandwidth: 131.38 KiB/s
Top used bandwidth: 250 KiB/s
Bandwidth rate: 4000 KiB/s
https://atlas.torproject.org/#details/B918EB3FA4D03A4F9F632AA17F217A6C04044EF7
Now used bandwidth: 1 KiB/s
Advertised Bandwidth: 82.65 KiB/s
Top used bandwidth: 245 KiB/s
Bandwidth rate: 800 KiB/s
https://atlas.torproject.org/#details/DF1C6C645C5854780778A3E81D12F2A8FF65744B
Now used bandwidth: 1 KiB/s
Advertised Bandwidth: 62.29 KiB/s
Top used bandwidth: 7 KiB/s
Bandwidth rate: 3000 KiB/s
https://atlas.torproject.org/#details/E2AF5879F39FF40DF8994E9B8FAEAB2518AEEBA4
Now used bandwidth: 1 KiB/s
Advertised Bandwidth: 70.94 KiB/s
Top used bandwidth: 916 KiB/s
Bandwidth rate: 1000 KiB/s
As you can see, most of them can handle a lot more traffic: 50x-4000x.
Also don't see why they can have high latency.
Good relays, on my opinion.
> But we know there is a bias in Tor's measurements towards North America
> and Europe, because that's where most of the measurements are made from:
No, this have no impact in this case.
I have launched my own instance of BwAuthority and I see, that measured
"filt_bw" values are pretty close to "Advertised Bandwidth":
node_id=$9FC2673BB2704C2AAB851F8334938565DF1D0819 nick=qq strm_bw=52732 filt_bw=77967 circ_fail_rate=0.0 desc_bw=134537 ns_bw=13000
node_id=$9FC2673BB2704C2AAB851F8334938565DF1D0819 nick=qq strm_bw=61278 filt_bw=70430 circ_fail_rate=0.0 desc_bw=85495 ns_bw=13000
node_id=$B918EB3FA4D03A4F9F632AA17F217A6C04044EF7 nick=TranTor strm_bw=40485 filt_bw=47052 circ_fail_rate=0.0 desc_bw=84635 ns_bw=12000
The problem is on the next step, I think.
>> The result has revealed some anomalies:
>> https://s8.hostingkartinok.com/uploads/images/2017/06/fed1cf8b57fc027223c8eaf3deb0d28a.png
>> First, and most important, - a lot of relays have bandwidth estimate
>> in range 0-50: 1082 of them.
> I don't know what each axis is on this graph.
x is KiB/s, y is count
(yellow bars are for "Advertised Bandwidth", blue - for
"Consensus Weight", grey mean both values)
> 20 is the default, 50 is the maximum for a relay's self-test.
> If a relay isn't measured, or measures very low, it usually gets a
> figure in this range.
I have excluded non-measured relays from this histogram.
>> Second - there are incorrect estimates
>> for popular bandwidths of 5, 10 and 20 MBits.
> I don't understand what you mean here. The advertised bandwidth is in
> kilobytes per second, and the consensus weight is dimensionless (but
> scaled from kilobytes per second).
> Can you point out the lines you mean?
Look at the yellow spike at x = ~1200.
Low blue bars at the same point means that "Consensus Weight" model
did not take into account that there are many 1200 KiB/s nodes on
the network, which will result in theirs underload.
-- Vort
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