File sync, star with slow channels?

Question

Data synchronization

I'm asking for help from the community, maybe someone will tell you something sensible.
The essence of the problem:
There is a Central Office and there are Branches.
The central heating center has a normal channel, the branches are conditionally sitting on gprs modems (the incoming one can still be corrected by satellite outgoing in any way), that is, slow periodically falling channels.
Let CO and F have white IP addresses.
It is necessary to establish the exchange of files between the CO and F in the background (without user intervention) according to the schedule (at least according to the Windows scheduler).
In the central office there are 2 folders (in out I think it's understandable) with the name of the branch in each branch with the corresponding name of the central office.
Some software periodically puts out in the desired folder and takes it from in.
Everywhere Windows Server 2008 (let r2) is not necessary to choose.
Actually the question is what to choose for the organization of transmission through such "good" channels? It is clear that the files will be compressed and encrypted, but I would not want to transfer them openly.
I think it makes no sense to raise a VPN, I'm afraid of overhead, but you need to save every bit per second.
I look towards cygwin ssh+rsync. Can someone suggest a more elegant solution, preferably natively Windows, or some kind of software package for sane money?
Can look towards SFTP, then the question is what kind of software? Maybe there are P2P solutions?

Answer 1

DFS?