APPROVED FOR PUBLIC RELEASE

This report presents testing and improvements to a protocol, rsync, for the synchronisation of similar data files in different locations. When copying a file A at location a to a remote location ß it is often the case that A has much in common with some data file B already stored at ß. In this situation rsync may be used to effectively send File A from a to ß in such a way that much less data than that contained in A is transmitted. Moreover this is achieved without requiring both files to be located at either a or ß. This paper provides new checksum functions that offer significant improvements over the existing functions, and proposes that checksum sizes be adaptive based on a verified model of the required checksum size