From : George Herbert <email@example.com>
Option 5: Provider X can announce nothing outside the area, except
to people who are paying X for transit to all X-reachable sites
This would work great if all the backbones touch down in the area.
Customers out in the Rest of the World get transit through their
backbone to all the area sites. Other regional networks or areas
get transit to it via whomever they get global transit from.
Which works fine as long as only one area on the planet ever implements
Option 5. Any pair of such areas without internal connectivity won't
be able to talk.
Seems like a scaling problem.