Before revision:  Furthermore, our state-space collapse result implies an interchange of limits as a by-product for the diffusion approximation by Vlasiou, Zhang and Zwart (2014) .
After revision:  Furthermore, our state-space collapse result implies an interchange of limits as a by-product for the diffusion approximation of the equal-weight case under phase-type file-size distributions, demonstrating the heavy-traffic insensitivity of the stationary distribution .