“Wouldn’t it be better to simply load only the changes from one page to the next? In many pages, the changes from one page to the next may be just a kilobyte or two of text, saving literally hundreds of Kb of bandwidth on every page hit. Loading only those changes would make your network guys very happy.
Well, that’s exactly what MDS tries to do. What the MDS does is that it allows users to load only what changes between pages. This drastically reduces page load time and speeds up responsiveness for the entire application.” please read more in http://blog.furuknap.net/minimal-download-strategy-in-sharepoint-2013
Mai Omar Desouki 