Hello, many of you (or maybe not) may know I do VoIP consulting among many other things. Like three years ago, in my one of my ex-jobs, I was asked to find a way to have an affordable VoIP cluster. I must say that was not easy; at that moment the only way to do that was with expensive solutions (some proprietaries, others open source), but at the end of the day, you need to pay expensive consulting time, not to mention you were chained to that vendor for life.
I have chosen FusionPBX to use as the WEB frontend of FreeSWITCH for many reasons I won't explain here, but you need to trust me that it is easy to install and to learn. So, using FusionPBX and some mutual help with the author of FusionPBX we developed the load balancing feature in FusionPBX. This feature allows more than one FreeSWITCH box to be aware of their other peers. This will allow a user register in server A to dial to a user registered in server B. FusionPBX (exactly the XML handler within) will know if the user is local or not and it will allow you to link. Think of the possibilities, one PBX in the USA, other in France and everybody able to communicate themselves unaware where they are registered.
Another cool thing on this, using the Smart DNS is that users will hit always the closest server. Users in Canada will hit the server in the USA, Users in the UK will hit the server in France. And, if for a reason, France server goes down, users will be forwarded to their best second option. Maybe my example is not the best, but think of big countries, it is not the same to be in Vancouver, Canada than Montreal, Canada, especially if you are going to connect to a server in NY, USA.