EF-S Zoom Markings

I'm going to assume this question has been covered a couple of times already, but I couldn't phrase the search query right to find a previous post.

On an EF-S specific lens (e.g. EF-S 17-55mm f/2.8), do the zoom markings correspond to the crop sensor or FF?  In other words, is 17mm really 17mm on a 7D/60D or is it really ~27mm (17*1.6)?

Thanks.