The login servers are in Japan. and yet manage both datacenters. This is why you see a snowball effect that JP prime will take down NA/EU's Lobby and NA or EU prime will take down the JP Lobby.
Couple this with letting people retry instead of actually using the queue system, and you have a couple orders of magnitude more traffic hitting that single (from an atechnical perspective) login server than there should be, leading to this cascading failure tendency. If they would ensure the queue worked and people weren't spamming reconnects every four seconds they'd not only make logins less 'spam and hope' but also reduce and stabilize their server load!
____________________________I've seen things you people wouldn't believe. Airships on fire off the shoulder of Bahamut. I watched Scapula Beams glitter in the dark near the Three Mage Gate...
There's always...not trolling him?
You're new here, aren't you?