2. Software-defined networks
Data center networks have grown calcified over time. While servers and storage have benefited from software abstractions, networks have remained hardware-bound and static, making them a major roadblock to cloud computing. Enter SDN (software-defined networking), which drapes a software layer over switch and router hardware to serve as both a centrally managed control plane and a platform for innovation.
SDN isn't network virtualization; rather it is a way to "program the network" -- that is, it allows cloud providers and ISVs to build new networking capabilities the rest of us can draw on. The leading example of SDN today is OpenFlow, the brainchild of university researchers who wanted to experiment with new network protocols on large production networks.