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Cisco software-defined networking: OpenFlow alone 'will not cut it'

OpenFlow will play a tiny role in the Cisco software-defined networking strategy, which will focus on making existing Cisco networks programmable. OpenFlow supporters are wary.

OpenFlow will only play a small role in the Cisco software-defined networking strategy. Instead, Cisco will focus on making existing networks more programmable by opening up IOS and NX-OS for third-party development. Also, Cisco will apparently not replace distributed protocols and forwarding with an abstracted centralized OpenFlow control plane.

But proprietary software-defined networking (SDN) methods will hamper the evolution of an innovative open-source network application development community, OpenFlow stalwarts say. OpenFlow can do more than centralize the control plane of the network for granular management. Third-party developers can create applications, such as orchestration, security and mobility management, which can work on any OpenFlow-based network regardless of vendor.

Matt Davy, chief network architect at Indiana University and executive director of interoperability lab InCNTRE, says proprietary SDN approaches are not likely to experience broad-scale success.

"I am not going to invest $2 million developing applications that only work on JunOS or IOS," Davy said.

In two years, Davy will launch a 100,000-port refresh of his university's network that will be OpenFlow-based. By the time his RFP process begins, he expects all of the major vendors, including Cisco, to have an OpenFlow option, and he won't consider those that don't.

Cisco software-defined networking strategy: intelligence will remain distributed

Cisco is a member of the Open Networking Foundation (ONF) and a major technical adviser to the development of the OpenFlow standard, but Cisco execs say their customers aren't looking for a software-defined networking strategy that will force a full network rip-and-replace.

"We have to connect realistically with what our customers want … in the short term, the majority of inquiries are coming from universities where they are funded to do OpenFlow research," said Shashi Kiran, senior marketing director for data center and switching.

Companies with huge amounts of data like Google, which revealed this week that it had built its own OpenFlow-based switches, have the resources and need to revamp networks, said Kiran. But most enterprise customers don't want to toss aside networks they've already built and know how to run, he said.

What's more, using OpenFlow to decouple the network control plane and make centralized forwarding decisions "will not cut it" alone when it comes to network programmability and virtualization, Kiran said. Instead Cisco will pursue a "multi-prong approach" that pulls together the virtual and the physical networks by keeping intelligence distributed throughout the switches in the network, while consistently collecting and analyzing that data in a centralized view to make policy and management decisions. Along with that, NX-OS and IOS would be open for users to develop applications or network services. A protocol like OpenFlow would only play a small role in this type of system. In fact, he added, there are other protocols, including some from the IETF, that play a role in how these third-party applications could talk to the network.

It remains to be seen what kind of products will result from Cisco's SDN strategy, but the company is expected to unveil an SDN portfolio at Cisco Live this spring. It is unclear whether that will include a controller or new switches.

Kiran did confirm that Cisco switches would eventually be OpenFlow-friendly so that customers can choose that as an option, depending on need. However, he expected that OpenFlow would run in a hybrid network alongside traditional protocols. Cisco is part of a new Open Networking Foundation hybrid working group, which is examining how to introduce OpenFlow into legacy networks one stage at a time, said Dan Pitt, ONF executive director.

Using OpenFlow and SDN to better manage existing network topologies, as Cisco is suggesting, would prevent an OpenFlow-induced commoditization of network hardware that many experts have predicted. Once OpenFlow is developed, it could basically run on merchant silicon and commodity components. But this would only undermine the value of hardware innovation, Kiran said.

What's so bad about not going OpenFlow?

Even the most fervent OpenFlow supporters admit there are numerous approaches to SDN that merit exploration. But Kyle Forster, CEO of BigSwitch Networks, a provider of OpenFlow-based SDN architecture, says, "Taking technologies that are five or six years old and calling them SDN is SDN-washing" and will only stifle innovation.

Cisco is not the only networking vendor that is both involved in ONF OpenFlow research and working on proprietary SDN methods. Arista's EOS is software-defined and proprietary, and Juniper's QFabric is basically a closed SDN approach.

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