It has been said that the shift to a virtual data center will be the most significant IT transformation since the invention of the mainframe. This transformation promises to join virtualized computing and storage layers to a virtualized network stack, while enabling new agile models such as cloud computing. At the same time, it is vital for the success of this technology that the transition to the virtual data center does not bring back the proprietary restrictions and limitations that were the hallmark of the mainframe era.