In a previous post I already mentioned Binary Differential Replication (BDR). In this post I will also show how to configure it. ConfigMgr 2007 can use BDR to update package source files with a minimum of additional network traffic. When ConfigMgr 2007 updates the source files for a package, and uses BDR, it sends the parts of the package that have changed since the last time the package was sent. So BDR will work after the source files have already been distributed. This minimizes the network traffic, especially when the package is large and the changes are small. A file is considered to be changed if it has been renamed, moved, or its contents have changed.
BDR will work as long as a site has a one of the previous five versions of the package. The originating site keeps track of the differences between the current version and the previous five versions. 
If a site has an older version of the package, the originating site will send the entire package.
How to enable Binary Differential Replication
- Open the Configuration Manager console and browse to System Center Configuration Manager > Site Database > Computer Management > Software Distribution.
- Select a Software Package and click in the Actions pane Properties to open the <Software Package> Properties.
- Select the Data Source tab and check the Enable Binary Differential Replication checkbox (see the picture).
BDR has to be enabled on every single Package.