If you were going to setup four separate networks for a client, geographically distributed throughout the world, how would you best handle load balancing between the four locations to ensure that people get the best connections and best performance? Certainly round robin DNS is simple enough, while anycast would be a good solution, it's not typical for global load balancing. While there are a few open source dns server options that do load balancing and geo targeting, none seem really enterprise levels. So how would you setup such a network?
I would look into using F5 BIG-IP for enterprise level. It probably isn't the cheapest option but for reliability it can be worth it.