In many settings, the OpenFlow protocol will gradually displace the frequently used spanning tree protocol, which applies a hardwired answer to the question of what route and on what type of network a particular message should travel. OpenFlow requires the network hardware to look more like a blank check than a payroll check. The network controller under OpenFlow will periodically write in the intended recipient and other delineators.
With such a method, IT teams may take many different approaches to their existing network hardware. A super-secure network can be designated and separated from all links to the Internet. High-capacity or low-capacity, high-latency or low-latency networks can be constructed, on top of the existing hardware resources, Casado explained.
Even in a jumble of mixed hardware, each network has its own address space, security configurations, statistics gathering and capacity management, managed by an automated controller, not human hands.
Lew Tucker, CTO of cloud computing at Cisco, has eloquently described to me the possibility that a virtualized network could recognize the nature of the application that's been brought to it, and respond with appropriate services.
Casado agreed that scenario is likely, but he said such an approach would be an engineered subsystem brought to the Quantum framework, not the framework itself. What the Quantum part of OpenStack is attempting to accomplish is putting a programmable, vendor-neutral interface between a human network manager and the network.
"The operational interface to the network has always been a proprietary one for the last 20 years," said Casado. Quantum in OpenStack will provide "a vendor-neutral one. You can slot in whatever network services you want" and even dissimilar services can function alongside each other on the same hardware because they're run through programmatic instructions or rules put into the governing code.
Whoever is managing this programmatic interface will be in a strong position to manage the whole private cloud. If the neutral perspective remains absent, the private cloud will never quite function in the way it was conceived. OpenStack and VMware are both competing to provide the virtualization management platform for the private cloud.
But since VMware joined OpenStack, the benevolent view is that both have reason to support Quantum's development. Without Quantum, OpenStack doesn't offer a complete private cloud because it can't handle virtual networks. In a similar vein, without Nicira, VMware can't build out the software-defined data center and its version of private cloud. The idea of private cloud founders on the customer's lack of virtualized networking. If VMware products don't always serve as the basis for private clouds, it's placing a bet on OpenStack as the runner-up.
Asked about VMware's commitment to OpenStack, Casado said: "It is important that we support our customers deploying on OpenStack and other open source technologies ... We plan to continue the contributions made by Nicira and Cloud Foundry ... add support for customers who choose to run (VMware) vSphere in OpenStack environments, and help shape the future of OpenStack and the value delivered to our customers by being an active participant [in OpenStack]."
Some question how benevolent VMware can afford to be. Boris Renski, co-founder of OpenStack consulting group Mirantis, voted against VMware joining the OpenStack project as a gold member, for which it pays $200,000 a year.