[VladVladikoff]

If I understood the post the author just takes the location of smallest ping as the winner. This seems like a very rudimentary approach. Why not do triangulation? If you take each ping time as a measurement of distance between two points, you should be able to ping from a random selection of IPs and from there calculate the location.

[jimaek]

I talk a little about it in the article, but the main goal was to build something simple that works as proof of concept.

This brute force approach works much better than I expected as long as you have enough probes and a bit of luck.

But of course there are much better and smarter approaches to this, no doubt!

[tomtomtom777]

How did you know how well these results work?

You mention the quality several times in the article but it's not clear how this is verified. Do you have a set of known-location-ip-addresses around the world (apart from your home)? Or are we just assuming that latency is a good indicator?

[jimaek]

I run about 270 servers in verified locations as part of the Globalping network https://globalping.io/users/jimaek so I had plenty of targets to test

I tested against them, as well as other infrastructure I control that is not part of the network, and compared to the ipinfo results as well

[direwolf20]

Packets don't travel in straight lines.

[coffeeri]

This is/was also my take. I’m skeptical that a probe-based network can be granular enough to reliably pinpoint a city, especially when some paths are much better connected than others (fewer hops, uncongested fiber, no throttling).

However, ipinfo still appears to rely on active probing to triangulate geolocation data, which suggests they believe these routing asymmetries can be modeled or averaged out in practice.

https://ipinfo.io/blog/ipinfos-probe-network

[direwolf20]

I think the idea is that if you have enough probes, one of them will be in the right location and network.

Tier 2 ISPs have the right incentives to peer with every network in every peering point, so you are likely to get a correct result from a different ISP. Tier 1 ISPs avoid peering, so if your probe or target is on Deutsche Telekom or Cogent, your packet takes a circuitous route, passing only through networks that paid the extortion money.

Friends don't let friends get internet service from Deutsche Telekom or Cogent.

[toast0]

It depends on the city, and how the ISPs in the city work.

The telco DSL and fiber in my metro area all runs through a single location where the PPPoE (hiss) concentrator is and the first hop latency from DSL interleaving swamps the latency from distance. You can someone is in the metro area, but not the county or city.

Cable company customers are a little more locatable, probably get the county.

[jofla_net]

yeah, when i used to live in New England, and had more time to be interested in transit, i always was peaked in how comcast would route. No matter how far south i seemed to get, i'd always need to travel to Boston's peering point first to make it to NYC, even in New Haven. If you then simply switch isps, even at same address, verizon would send you south immediately.

so theres funky overlap wherein on one isp you appear closer to city A, and on isp 2 closer to city B, but its same physical address.

Continental classification I'd think would be good as they appear to be coalesced endpoints, separated by vast oceans.