I am creating an SVG data panel, so far:

Its very much a work in progress, hence the commented out bits. I want to create a panel that is a rectangle with rounded corners, I am trying to add highlights and shading to the rectangle to give a 3d appearance.

The horizontal and vertical parts are easy enough, its the missing curved bits I need help with, I'm trying to learn how path works, to create a curve, can anyone help?