Prioritize network usage by app?
Implementing quality of service on the network client/endpoint is generally a waste of time and therefore (I presume) no one has made that sort of software for OS X.

There isn't an easy way to go in and fiddle with things without tearing down the transfers that are in progress and I can probably infer that you can't resume either transfer easily or you would have simply paused the first to see if it helped the second already.

A more viable option going forward is to use a network protocol that lets you pause one and resume a partial transfer for the long acting transfers.


transmit.app allows you to pause transfers
rsync effectively allows you to resume transfers since it can pick up a partial transfer in the middle of a large file when it gets interrupted.