I think it's very related topic. In my practice I regularly find mislocated probes and report them to RIPE because I don't have a way to contact directly with host. RIPE on the other hand can only politely ask host to update location. It's volunteer project after all. Of course majority of probes are marked correctly, otherwise whole project would be just a waste of time. Still,

Another related topic of probe locations is Hong Kong. Some probes which has pins in Hong Kong have country set to China and some to Hong Kong. Apart from political problems, it's important to reliably distinguish Mainland China and Hong Kong SAR because from routing/Internet point of view these are on two different worlds on opposite sides of Great Firewall of China. It means that I have to manually select probes when I want to measure Mainland China or Hong Kong.

Regards,

Grzegorz

From: Massimo Candela <massimo@us.ntt.net>
Date: Thursday 2021-03-25 at 14:03
To: "ripe-atlas@ripe.net" <ripe-atlas@ripe.net>
Subject: Re: [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