[atlas] Probe location obfuscation

[possibly OT]

In 2018 we found 18 probes which were located so far from reality that 
the collected RTT towards targets of known locations was faster than the 
speed of light (I remember we did something about those). I suspect 
there are some cases more, just below speed of light. But not so many, I 
believe the vast majority of the probes are all set properly.

With software probes there is also the problem of less users reporting a 
location at all (I don't have numbers, based on an observation in a past 
experiment. It may no longer be the case).

I don't remember if there is something similar already in place, but I 
would suggest a process like:
- if a probe doesn't have a location, set a location calculated by 
latency measurements AND ask the user to review the result at is first 
convenience;
- for all the probes currently having a location, use latency 
measurements to mark the one possibly wrong and ask the user for update.
- overall, use latency measurements to periodically review the probe's 
location. RTTs can be used to mark obviously wrong locations, without 
being too restrictive.

For RTTs above a certain amount (the usual 10ms?), deactivate the RTT 
validation so users are still able to place probes in exotic locations.

I don't think there is a use case for obfuscating probes more than at 
the city level. And if there is, these probes should be tagged as such.

Ciao,
Massimo

On 25/03/2021 13:00, Ponikierski, Grzegorz via ripe-atlas wrote:
> I would add to it additional problem that some hosts obfuscate probe 
> location even more. For example you can find probes which in reality are 
> located in US but are marked as CN or probes which are in reality in 
> Wisconsin but are marked in California. Of course these are extreme 
> cases. I guess most hosts just put a pin with probe location just 
> somewhere around where it's locate as long it's in the same city. I 
> don't remember, as a host of 3 probes, to get any precise 
> recommendations how to mark probe location. Personally I just put a pin 
> in city district where probe is locate.
> 
> Regards,
> 
> Grzegorz