"We have MAC addresses in the millions, potentially" from virtualization, Cheng says. "That scale is beyond what any reasonably constructed switches can comprehend."
Some Brocade competitors and fellow ONF members are a bit more bearish on OpenFlow, though. Force10 is waiting for the technology to mature a little bit more before offering it in its switches, says Chief Marketing Officer Arpit Joshipura.
"We have to make sure that all the specifications that were originally not scalable are scalable," Joshipura says. "Big network users are more interested in this today than traditional enterprises."
And still others outside the ONF say OpenFlow may be reinventing the wheel.
"We did 'experiment' with such an architecture already in the early '90s, where we tried to centralize flow setup decisions centrally with a system called SecureFast VNS Virtual Network Server," says Markus Nispel, chief technology strategist at Enterasys Networks, a Siemens Enterprise Communications company. "Due to scalability problems this ended up in a released product/architecture called SecureFast which used a distributed flow setup and was also connection-oriented switching leveraging 'OSPF on L2' as the topology protocol. Which gave us ... active Layer 2 meshing in 1996.
"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."
he 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."
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