[tor-bugs] #27337 [Core Tor/sbws]: Round relay bandwidths in bandwidth files

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#27337: Round relay bandwidths in bandwidth files
---------------------------+-------------------------------------
 Reporter:  teor           |          Owner:  (none)
     Type:  defect         |         Status:  new
 Priority:  Medium         |      Milestone:  sbws 1.0 (MVP must)
Component:  Core Tor/sbws  |        Version:
 Severity:  Normal         |     Resolution:
 Keywords:                 |  Actual Points:
Parent ID:                 |         Points:
 Reviewer:                 |        Sponsor:
---------------------------+-------------------------------------
Description changed by teor:

Old description:

> Torflow rounds raw bandwidths to 3 significant figures, and increases 0
> bandwidths to 1:
>
> https://gitweb.torproject.org/torflow.git/tree/NetworkScanners/BwAuthority/aggregate.py#n62
>
> Rounding
>
> sbws must round to 3 (or fewer) significant figures, so that consensus
> diffs are still efficient.
>
> I suggest 2 significant figures, because the largest error is 5% at
> 1.5*10^n^ (for example: (105-100)/100 = 5%).
>
> Bandwidth authorities already vary from each other by 25-50%:
> https://trac.torproject.org/projects/tor/ticket/25459#comment:5
>
> And network load varies each day (from what I remember, my guards and
> exits used to vary by at least 10% every day).
>
> Avoiding Zeroes
>
> I think sbws should also increase 0 bandwidths to 1.
>
> We also have to update the spec, I'll open a child ticket.

New description:

 Torflow rounds raw bandwidths to 3 significant figures, and increases 0
 bandwidths to 1:

 https://gitweb.torproject.org/torflow.git/tree/NetworkScanners/BwAuthority/aggregate.py#n62

 === Rounding ===

 sbws must round to 3 (or fewer) significant figures, so that consensus
 diffs are still efficient.

 I suggest 2 significant figures, because the largest error is 5% at
 1.5*10^n^ (for example: (105-100)/100 = 5%).

 Bandwidth authorities already vary from each other by 25-50%:
 https://trac.torproject.org/projects/tor/ticket/25459#comment:5

 And network load varies each day (from what I remember, my guards and
 exits used to vary by at least 10% every day).

 === Avoiding Zeroes ===

 I think sbws should also increase 0 bandwidths to 1.

 We also have to update the spec, I'll open a child ticket.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27337#comment:1>
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