The rsync program of the rsync algorithm is unsuitable for this, primarily because it requires a lot of server-side resources. However, the zsync implementation works around this: the server is a standard HTTP server, and a new data file is added (containing the rsync "signature" data). All the rest of the computation will then happen on the client, which uses HTTP Range requests to fetch parts of the file from the server.
The RPM world has presto, which relies on the package archive generating delta-RPM packages. These are then downloaded normally, and applied by the client differently from normal RPMs. This requires upgrades to happen from a specific version, which the rsync/zsync/apt-sync approach avoids.
Dark Star said:^^Do post the video..