When it comes to thinking about the future data center, it's well understood that servers and storage will function as pools of virtualized resources that can automatically switch from task to task.

Networking is a much harder nut to crack. It remains unvirtualized and has lagged far behind the other two. But without it, we'll never get to the flexible, automated data center of the future envisioned as a "private cloud."

That's why I sat down to talk to Martin Casado, the former Stanford grad student whose PhD thesis turned into the OpenFlow networking protocol. Casado co-founded virtual networking firm Nicira, which soon became the lead contributor to OpenStack's virtual networking project, Quantum. VMware bought Nicira for $1.26 billion in July -- not bad for a young company with 100 employees.

I'd asked Casado to explain how Nicira was going to continue to lead development of virtual networking in OpenStack, since open source OpenStack competes directly with VMware to manage the virtualized part of the data center that's implementing automated self provisioning, elastic expansion and chargeback -- the private cloud part.

[ Want to learn more about why VMware acquired Nicira? See Nicira Acquisition Is VMware's Smartest Move Yet. ]

VMware now has a lot of influence in OpenStack. The Quantum project's technical lead and elected chairman of the development team is Dan Wendlandt, who had been a Nicira designer and software team leader and now is a senior product line manager at VMware. Casado is now chief architect for networking at VMware.

VMware, of course, is the most likely candidate to become the kingpin of proprietary private cloud through its vCloud Director and vCloud Suite. And that makes it OpenStack's chief competitor in establishing private clouds inside the enterprise. After listening to Casado, a virtual networking enthusiast, I felt I understood how these dissimilar pieces -- proprietary product line and open source code contributions -- fit together. But be your own judge.

First, Casado says Quantum is not a particular set of networking features or a new kind of switch/router/controller hardware combination. It is "a framework of open interfaces you use to build up virtual networking for a software-defined data center or a cloud."

Without virtual networking, the virtual machine's connection to a network is buried as a software switch in a hypervisor. That software switch can be made more efficient by offloading its work to a nearby hardware fabric, as HP and Cisco do. But it would be easier if the compute server, storage and networking could all be virtualized upfront as a pool of resources, with shares of capacity "snapped together" when a virtual machine is created. "Quantum provides the virtual network platform and OpenStack provides the harness where all three fit in," said Casado.

The network virtualization platform embeds route-building and capacity-assigning capabilities into a network controller, or distributed controllers, which manage on a dynamic basis the network switches and routers. (Nicira offers commercial software with the name Network Virtualization Platform). A network management console allows instructions to flow from network administrators, or virtual machine administrators, to the controllers. If the size of a virtual server needs to be increased to match its growing traffic load, the network can be increased at the same time.

Both Nicira products and the Quantum framework follow the principles incorporated into the OpenFlow standard, which was developed as a cooperative effort between advanced networking groups at Stanford and Berkeley. (How often does that happen?)