Drupal does not support download resume , meaning that downloading large private files can be troublesome because if for any reason the download fails , there is no way to continue downloading from where it stopped and the whole file should be downloaded again.
NOTICE : This module does not need any patch to work
NOTICE : Please join and contribute if you're interested to have this useful feature in core :
* Multi Part/Section file download
* Resumable file download
* Download speed limit support
* Automatic client download abort detection