DFS Replication is a Role of Windows Server that can use it to replicate File Servers across LAN or Internet.
DFS (Distributed File System) Replication use a compression algorithm as remote differential compression (RDC) to replicate only the changes in file block instead of the entire file. If you need more details you can find in Technet https://technet.microsoft.com/en-us/library/jj127250(v=ws.11).aspx.