Do a tracert to your datacenter then ping continuously each part of the route and check for packet loss.

If you get 100% packet loss at part of the route, it's probably because it's not responding to pings so you can ignore it.

But if you get responses and then you see gaps with no responses, that's packet loss.

Then you have to figure out who owns that part of the route. Is it you? Your Internet service provider? Square Enix's Internet Service Provider?