[atlas] Communication with probes' owners

On 24/04/2019 19:20, Ponikierski, Grzegorz wrote:
> Thanks everybody for comments and interest :)
> 
>  
> 
> When it comes to security and spammers I think that you can approach to
> it like to any PM feature available on any message board. I think it's
> natural for any community to be able to communicate with each other.
> After all RIPE Atlas is a community of networking geeks/nerds/engineers
> who like to measure the Internet and share resources with others.
> Sometimes we just need to exchange some info to get help and mailing
> lists is not always the best way to do it. I don't think it's a serious
> security threat but I also find comments from Martin Boissonneault quite
> helpful to build something as much secure as possible without excessive
> complexity.
> 
>  
> 
> When it comes to location of probes, Steve Gibbard probably described
> the real problem more precisely than me. The goal is to get reliable
> data about probes location and this is for sure important for all RIPE
> Atlas users. One way is to poke people manually and it's OK if you have

As someone who uses RIPE Atlas at scale, i fully agree. Probe location
accuracy is an important data quality issue in RIPE Atlas. Wrongly
located probes are a big source of weirdness in things like
ixp-country-jedi (
https://www.ripe.net/analyse/internet-measurements/ixp-country-jedi ).

> to do it once per few months but it would be better to get more
> automated detection mechanism for that. Steve uses IP geolocation which
> has its limitations (I know probes with IPs from country X but they are
> properly deployed and described in country Y on different continent). I
> personally visualize distance from probe to target and compare it with
> RTT and hops but it's still not fully automated and still can be tricky
> and requires additional checks.

I've also seen the limitations of (Maxmind) geolocation. and i would say
it's very hard to find good guidelines on when Maxmind geolocation is
better or worse then what probe hosts provide.

> So open question is: How to reliably verify location of probes OR How to
> motivate RIPE Atlas users to provide valid locations and keep it up-to-date?

What i've seen for many cases of incorrectly geolocated probes is that
this was caused by probes being physically moved (because the person
hosting the probe moved to a different city, possibly country).
One thing i've briefly looked into is if we can use a change of ASN that
we see the probe in as an indicator that the probe host should be sent a
reminder to check if the probes geolocation is still correct. This
turned out messier then i thought (too many probes seem to cycle through
two or more ASNs), but we can revisit this idea and see if we can make
this work as part of a process to counter wrongly geolocated probes.

Another thing i looked into is using similarity between probes as an
indicator of wrong geolocation. Intuition is that if 2 probes see the
same IP path to a destination, they are probably topologically close to
each other, which typically means they are physically close (but not
always, eg. tunnels). So if we see 2 probes that are topologically
close, but physically very distant, that probably means either a wrong
geolocation or an 'interesting' setup of one of the probes.
See table 1 (and text below) of
https://archive.psg.com/170602.anrw17-paper9.pdf

hope this helps,
Emile