Synchronizing the sync server with the server

I have a script like this:
script http://i.msdn.microsoft.com/bb887608.Figure3(en-us).png
Here I need to synchronize the local server database with the main database server (for example: computers in the office are connected to the office server, and they use it as a local server, so no synchronization is required. BUT computers in the other office work with their local server too and we need synchronization between offices, although the main database server.). As I can see, I cannot use SQLCompact here. Is there a provider that does server-to-server sync directly from the client? If not, can someone provide a sample solution on how to manage such a situation?