Is it possible to throttle the iCloud photostream sync in OS X?

I have a large iCloud photo library. Once in a blue moon my iMac running Yosemite decides to forget all about the synced libraries, and I have to re-enable the iCloud streams. However, my little DSL line will then be clogged for hours on end, because OS X downloads gigabytes of pictures.

Is it possible to throttle the speed to a certain setting, say 1MBit/sec? Or at least to pause the sync, without having to re-download everything?