So I can't play and tell with EU/NA/JP friends in ARR...

[AarosLunos]

Well now your contradicting yourself. That's an illustration of interconnection and peering of autonomous systems and you said the solution was a leased line. That illustration has literally nothing to do with this discussion.

You may also be interested to know that leased lined only exist in USA, UK, India, Hong Kong, and Italy.

Incorrect leased lines can be built as virtual circuits attached to a physical interface. So they can be bundled over one physical medium and specific traffic shaping rules assigned. They are used all the time for over trans-oceanic fiber. I've configured plenty for domestic AND international clients.

It doesn't matter what the physical medium is since its piggy backed onto a physical interface at the router level. Its one of many ways to optimize routing. BGP route announcements (public and private) and leased lines can and often are used in conjunction. One common use is reducing the number of routers your traffic passes through while announcing your public IP address space to both ends of the leased line. BGP in itself doesn't optimize routing. That is done through peering agreements. BGP just announces the that addressable IPs are attached to a specific AS.

IF SE has peering agreements with specific providers it is possible they can change their BGP announcements to reduce latency without a leased line between the two other data centers. It just really depends because its situational.

I know that despite increasing evidence that I clearly know what I'm talking about, you won't believe me either way. If I wasn't bound by disclosure contracts, I would tell you specifically who I work for (HINT: Its a large backbone provider that is well known for pushing IPv6 roll out) But I'm not going to risk my career over a sniveling troll.