<i>zsync uses the rsync algorithm, but runs it on the client side, thus avoiding the high server load associated with rsync...All that is needed is an HTTP/1.1-compliant web server.</i><p>although it does require one thing on the server side it seems:<p><i>zsync downloads are offered by building a .zsync file, which contains the meta-data needed by zsync. This file contains the precalculated checksums for the rsync algorithm; it is generated on the server, once, and is then used by any number of downloaders.</i><p>Interesting idea for reducing bandwidth on large, frequently polled files.