[tor-relays] Questions about consensus votes

[Sebastian Hahn]

Hi Tobias,

thanks for running a relay!

> On 20. Apr 2021, at 15:21, Tobias Höller <hoeller at ins.jku.at> wrote:
> 
> I have only recently started operating relays (Family:008196DC449482C73CFA9712445223917F760921) and have some trouble with reliably getting the "Fast" and "HSDir" flags for my relays. Right now they regularly obtain and loose these flags and I would like them to be more stable To figure out what was going wrong, I took a look at the archived votes at https://collector.torproject.org/archive/relay-descriptors/votes/
> Unfortunately, I still don't understand why some things are happening, so I'm hoping you can help me out:
> 
> 1. The "Fast" flag is assigned by either measurements (if the DirAuth is also a Bandwidth Auth) or the reported bandwidth. On my relays I noticed that if I set the "BandwidthRate" close to the fast threshold (105KB/s) I would not get the fast flag, unless I configure a much higher bandwidth burst rate (>5MB/s). Even more confusing, different bandwidth auths seem to require different burst rates. While for example Moria1 started voting me fast with a Bandwidth Burst rate of 5Mbit/s, maatuska did not do so until I increased the BandwidthBurst to 100Mbit/s (my complete internet uplink). What I'd like to know: Is that something that only affects me or have you also experienced it? And are there any recommendations how high the bandwidth burst should at least be compared to the desired bandwidth rate?

It is quite natural that different dirauths will reach different verdicts, because they are all located at different locations around the world. Additionally, the exact cutoffs for the flags are somewhat dynamic depending on what other relays are doing - in general, there's no hard number that will definitely be enough or definitely won't be.

> 2. I am confused about the HSDir flag: According to https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n2500 it should require the relay to be fast+stable+ uptime>MinUptimeHidServDirectoryV2 (by default 96 hours). So, if an authority votes my relay to be Running+Stable+Fast for 100 consecutive votes, it should vote for "HSDir" in the last 4 votes, right?. Because moria1 for example, votes my relays to be fast+stable+running constantly, but never votes for the HSDir flag.
> Is there another condition for becoming HSDir that I am not aware of, or can you think of an other reason why this is happening?

Moria applies its own criteria which differ from dir-spec. Its operator is testing future improvements to the Tor network and therefore frequently doesn't follow all the specs.

> Lastly, I'd be curious to learn if I am the only operator who has trouble to maintain flags on their relays, or if you have also experienced similar problems to mine. If yes, how did you solve them.

Yes, some relays have this problem. In general I would recommend not worrying about the flags so much. Provide the most useful relay you can from a bandwidthrate perspective, keep it online, and that's already helping the network a lot.

That said, it is useful to see if the network as a whole is actually acting as designed. You seem to have invested quite a lot of effort already into dealing with flags, so perhaps that would be something that interests you more. Tor metrics might be a starting point if you wanted to go that route

Cheers
Sebastian