Ok, if you run a traceroute from both sides you can determine both paths (generally). If you use mtr or something like that along the way you'll usually see some "bright lines" in latency/loss/etc. Its not bulletproof but generally works.
That said - a peering agreement can have a variety of terms so a gamer isn't likely to be privvy to that. But if you see latency and loss on a certain link, you've likely identified the problem. Typically both parties are bound to solve it if its the actual peering link, a fair amount of the time its an individual ISPs problem so that ISP would be obligated to upgrade its internal link(s) to meet the demands of its customers.
Some time ago (2014) I convinced (forced under contract) a very large last-mile carrier to fix/upgrade its internal links after I browned out a few counties with my paid-for usage. Its not that hard, it just took a lot of phonecalls on my part and calls with our finance department... I guess the alternative was for them to let me continue browning out their customers for a section of the San Francisco bay area, having them ragequit and switching to someone else. Or wasting thousands and thousands of hours with customers complaining about terrible service.
I don't dispute that you can usually locate the link that's saturated if you can traceroute from both sides. I think we both agree that an end user can't figure out which end of the link is not holding up their end of the contract.
Good on you for getting a big telco to live up to their agreement. I doubt that lack of tenacity is the problem in cases having to do with large isp/video streaming/cdn players.
That said - a peering agreement can have a variety of terms so a gamer isn't likely to be privvy to that. But if you see latency and loss on a certain link, you've likely identified the problem. Typically both parties are bound to solve it if its the actual peering link, a fair amount of the time its an individual ISPs problem so that ISP would be obligated to upgrade its internal link(s) to meet the demands of its customers.
Some time ago (2014) I convinced (forced under contract) a very large last-mile carrier to fix/upgrade its internal links after I browned out a few counties with my paid-for usage. Its not that hard, it just took a lot of phonecalls on my part and calls with our finance department... I guess the alternative was for them to let me continue browning out their customers for a section of the San Francisco bay area, having them ragequit and switching to someone else. Or wasting thousands and thousands of hours with customers complaining about terrible service.