[Tor-BSD] This list...

Linus Nordberg linus at nordberg.se
Sat Jun 15 10:49:53 EDT 2013

George Rosamond <george at ceetonetechnology.com> wrote
Fri, 14 Jun 2013 13:10:37 -0400:

| > | Recreating a fingerprint on boot doesn't matter.
| > |
| > | While I don't generally do this on relays, what are the negatives about
| > | doing it on relays?  Yes, your fingerprint gets recreated and you lose
| > | any "credibility" as a relay.  And it then takes time to become marked
| > | stable or a guard.
| >
| > Meanwhile clients will not want to use your relay as much as they were
| > before you rebooted. IIRC it'll take you a week or two to gain Guard
| > f.ex. Pretty bad IMO.
|
| Well that is my question.  I know that you have to re-earn guard and
| stable status, but *how* bad is that?

>From [dir-spec]:

"Stable" -- A router is 'Stable' if it is active, and either its Weighted
MTBF is at least the median for known active routers or its Weighted MTBF
corresponds to at least 7 days. Routers are never called Stable if they are
running a version of Tor known to drop circuits stupidly.  (0.1.1.10-alpha
through 0.1.1.16-rc are stupid this way.)

To calculate weighted MTBF, compute the weighted mean of the lengths
of all intervals when the router was observed to be up, weighting
intervals by $\alpha^n$, where $n$ is the amount of time that has
passed since the interval ended, and $\alpha$ is chosen so that
measurements over approximately one month old no longer influence the
weighted MTBF much.
[...]
"Guard" -- A router is a possible 'Guard' if its Weighted Fractional
Uptime is at least the median for "familiar" active routers, and if
its bandwidth is at least median or at least 250KB/s.

To calculate weighted fractional uptime, compute the fraction
of time that the router is up in any given day, weighting so that
downtime and uptime in the past counts less.

A node is 'familiar' if 1/8 of all active nodes have appeared more
recently than it, OR it has been around for a few weeks.

| Is there a benefit in "diffusion" with more ephemeral relays?

Depends on what "ephemeral" means in that sentence I guess.

Moving a bridge around to different addresses and ports will make the
churn of bridges higher. That is a good thing for those trying to find a
bridge that works who are on a network where bridges are being blocked
on destination address and port. Some networks block on traffic
signature though.