[tor-dev] Raising AuthDirMaxServersPerAddr to 4?

[Roger Dingledine]

On Sun, Jun 02, 2019 at 10:43:14PM +1000, teor wrote:
> Let's deploy sbws to half the bandwidth authorities, wait 2 weeks, and
> see if exit bandwidths improve.
> 
> We should measure the impact of this change using the tor-scaling
> measurement criteria. (And we should make sure it doesn't conflict
> with any other tor-scaling changes.)

Rolling out more sbws measurers sounds good to me.

But, maybe I haven't been following, but isn't the first plan for sbws
to replace torflow but have identical behavior? And then we can work on
changing it to have better behavior?

I ask because in that case switching to more sbws measurers should not
cause the exit bandwidths to improve, until we then change the measurers
to measure better.

> If we do decide to change AuthDirMaxServersPerAddr, let's work out how
> many new relays would be added to the consensus straight away. There
> shouldn't be too many, but let's double-check.

$ grep "^r " moria1-vote | cut -d' ' -f7 | sort | uniq -c | sort -n

yields these IP address counts that have more than 2 relays on them:

      3 163.172.132.167 [only 2 actually Running]
      3 80.210.238.199 [it's a snap package, 0 Running]
      4 78.146.180.236 [only 1 actually Running]
      5 93.202.254.196 [0 Running]
      6 218.221.205.161 [they're all on the same port, 0 Running]
      7 212.24.106.116 [at least 4 Running]
      8 79.137.70.81 [0 Running]
      9 159.89.4.187 [0 Running]
     10 212.24.110.13 [at least 4 Running]

So I believe that if we change it to 4 relays per IP address, we would
get 4 more relays in the consensus currently.

And if we change it to 3 relays per IP address, we would get only 2
more relays currently.

Of course, once we make it clearer that big relays can run more instances
per IP address, some people might choose to simplify their set-ups.

--Roger