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Re: [tor-bugs] #27338 [Core Tor/sbws]: How long should sbws keep measured and observed bandwidths?
#27338: How long should sbws keep measured and observed bandwidths?
---------------------------+-------------------------------------
Reporter: teor | Owner: (none)
Type: task | Status: new
Priority: Medium | Milestone: sbws 1.0 (MVP must)
Component: Core Tor/sbws | Version:
Severity: Normal | Resolution:
Keywords: | Actual Points:
Parent ID: #27108 | Points:
Reviewer: | Sponsor:
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Comment (by teor):
Replying to [comment:5 juga]:
> Replying to [comment:4 teor]:
>
> > The minimum viable product must:
> > * Use the latest descriptor bandwidth limit, because:
> > - the latest descriptor contains the limit that the operator has
asked for
> > * Use at least 2 sbws measured bandwidths over at least 2 days,
because:
> > - tor relay usage varies on a daily cycle
> > - each sbws measurement depends on the time of day
> > * Use at least 2 descriptor observed bandwidths over at least 2 days,
because:
> > - a single download by a single client can increase the observed
bandwidth
> > - for security, we want results that don't depend on a single
client's behaviour
>
> Currently, it's possible that after 2 (or more) days we didn't collected
less than 2 measurements and descriptor observed bandwidths for some
relays.
> It's possible that prioritization might need some changes, which i think
might be related to https://github.com/pastly/simple-bw-
scanner/issues/136.
> If prioritization can't change that, it might be the case that is not
possible to obtain 2 measurements in the last 2 days.
Ok, I think those rules are confusing.
Let's try to split them up:
If any of these things are true, do not put the relay in the bandwidth
file:
* there are less than 2 sbws measured bandwidths
* all the sbws measured bandwidths are within 24 hours of each other
* there are less than 2 descriptor observed bandwidths
* all the descriptor observed bandwidths are within 24 hours of each other
We will need to make these settings configurable, so we can get test
network results in less than 1 day.
> > * Don't keep bandwidths for more than 1 week
> > - old bandwidths do not help us work out current relay capacity
>
> For bandwidth files, that's the default. Raw measurements are keep 90
days by default
Sorry, I meant:
* Don't use sbws measured bandwidths that are older than 1 week
* Don't use descriptor observed bandwidths that are older than 1 week
> > If you want, I can write or review patches, or write a detailed spec.
>
> I've already the code except for the comments above (need to clean a bit
commits). Reviews and spec would help.
Ok, when you finish a ticket, let me know, and I will do the review and
spec.
> > The descriptor has:
> > {{{
> > "bandwidth" bandwidth-avg bandwidth-burst bandwidth-observed NL
> > }}}
> >
> > Torflow does:
> > {{{
> > bw_observed = min(bandwidth-avg, bandwidth-burst, bandwidth-observed)
> > }}}
> > https://gitweb.torproject.org/pytorctl.git/tree/TorCtl.py#n459
> >
> > But that's redundant, because tor relays do:
> > {{{
> > "bandwidth" min(RelayBandwidthRate, RelayBandwidthBust, BandwidthRate,
BandwidthBurst, MaxAdvertisedBandwidth) min(RelayBandwidthBust,
BandwidthBurst) bandwidth-observed NL
> > }}}
> > See get_effective_bwrate() and get_effective_bwburst().
>
> i've been collecting and documenting all these possible values and the
different names they could have so i don't get confused.
> I've just not put that notes online somewhere yet but intend to do so.
Thanks!
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27338#comment:6>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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