Hi,
Juga and pastly have been working hard on sbws.
Sbws' results are now similar to torflow's results: https://trac.torproject.org/projects/tor/attachment/ticket/27135/20180826_08...
Now that sbws is close to torflow, we want some feedback on its design. We’ll work on the design at the tor meeting in September.
Please feel free to give feedback by email, or on the tickets:
What happens when sbws doesn't match torflow?
https://trac.torproject.org/projects/tor/ticket/27339
We suggest this rule:
If an sbws deployment is within X% of an existing bandwidth authority, sbws is ok. (The total consensus weights of the existing bandwidth authorities are within 25% - 50% of each other, see #25459.)
How long should sbws keep relay bandwidths?
https://trac.torproject.org/projects/tor/ticket/27338
Torflow uses the latest self-reported relay observed bandwidth and bandwidth rate.
Torflow uses a complex feedback loop for measured bandwidths. We think sbws can use a simple average or exponentially decaying weighted average.
How should we scale sbws consensus weights?
https://trac.torproject.org/projects/tor/ticket/27340
If sbws' total consensus weight is different to torflow's total consensus weight, how should we scale sbws?
(The weights might differ because the measurement method is different, or because scanners and servers are in different locations.)
In the bandwidth file spec, we suggest linear scaling.
How should we round sbws consensus weights?
https://trac.torproject.org/projects/tor/ticket/27337
Torflow currently rounds to 3 significant figures (which is a maximum of 0.5%). But I suggest 2 significant figures for sbws (or max 5%), because: - tor has a daily usage cycle that varies by 10% - 20% - existing bandwidth authorities vary by 25% - 50%
Proposal 276 contains a slightly more complicated rounding algorithm, which we may want to implement in sbws or in tor:
https://gitweb.torproject.org/torspec.git/tree/proposals/276-lower-bw-granul...
Does sbws need a maximum consensus weight fraction?
https://trac.torproject.org/projects/tor/ticket/27336
Torflow uses 5%, but I suggest 1%, because the largest relay right now is only 0.5%.
T
-- teor
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