"The main concern here is trying to externalize the flow setup," Nispel says. "10G Ethernet could bring you up to 15 million flows per second per interface. How could an external system cope with that? We do have hardware assistance internally to the system to manage flows in the system. External [would be] challenging."
Nevertheless, Enterasys is investigating a hybrid approach where only selective flow setups are done externally for application awareness and tracking, Nispel says. The rise of cloud services requires more intelligence and visibility into flows for security purposes, to enforce application policies and for more advanced application delivery services, he says.
But Nispel considers OpenFlow more of a service provider or specialized data center protocol than a general-purpose mechanism for the enterprise. There are enough established protocols available for separation of services in the enterprise, he says. Adding OpenFlow to the mix would overly complicate and confuse matters.
"I do see technologies like VLAN, VRF, MPLS and tunneling like GRE as established," he says. "You could add OpenFlow, but will it make it easier? I do not see that OpenFlow-based solutions are easier to deploy."
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The ease of deployment comes with the protocol's programmability, says Berkeley's Shenker.
"You program switches through scripting, the same way you can program everything else," Shenker says. "The technology is not limited at all; it's just providing programmatic control. You can manage the network so that each specific need is met."
Programmability was problematic before because vendors opened up their control plane functionality on routers and switches to varying degrees. Programmability was vendor-specific and device-specific, Shenker says.
ONF serves as a vehicle to ensure that this programmability remains consistent, easy to use and easy to access across various network devices from various vendors.
"We needed to standardize OpenFlow" for this to occur, Shenker says. "There needs to be an industrial-strength standards body. A few vendors offer it now, but there will be more by the end of the year."
Other observers feel external programming of routers and switches through OpenFlow and SDN could help IT shops better manage their data centers. In a post on his "OpenSource Fact and Fiction" blog, Alan Shimel writes that it could make it easier to traffic around hardware failures.