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Managing Editor

FAQ: What is OpenFlow and why is it needed?

Apr 14, 20112 mins
Data CenterEnterprise ApplicationsNetwork Switches

Frequently asked questions about the OpenFlow protocol and its potential

Frequently asked questions about the OpenFlow protocol and its potential.

What is OpenFlow?

OpenFlow is a programmable network protocol designed to manage and direct traffic among routers and switches from various vendors. It separates the programming of routers and switches from underlying hardware. It is the result of a six-year research collaboration between Stanford University and the University of California at Berkeley.


How does OpenFlow work?

The technology consists of three parts: flow tables installed on switches, a controller and a proprietary OpenFlow protocol for the controller to talk securely with switches. Flow tables are set up on switches. Controllers talk to the switches via the OpenFlow protocol and impose policies on flows. The controller could set up paths through the network optimized for specific characteristics, such as speed, fewest number of hops or reduced latency. .

Why is OpenFlow needed?

Vendors offer varying degrees of user programmability on their routers and switches. This can lead to limited functionality for traffic engineering and management, or inconsistent traffic management between equipment from multiple vendors. OpenFlow is designed to provide consistency in traffic management and engineering by making this control function independent of the hardware it’s intended to control.

Wasn’t MPLS designed to do this?

Yes, MPLS is a traffic management and engineering technique. But the programmability of the MPLS capabilities of a particular vendor’s platform is specific to that vendor. Also, MPLS can be a Layer 3 technique (and can also be Layer 2) while OpenFlow is a Layer 2 method, which has particular applicability to data centers. Many feel MPLS is overly complex as well and, while standard, could be implemented differently by different vendors.

When will OpenFlow be available?

A limited number of vendors are offering it now. Some others are expected to offer it later this year. Once the technology is standardized and promoted through the more vendors are expected to offer it on their switches and routers.

Managing Editor

Jim Duffy has been covering technology for over 28 years, 23 at Network World. He covers enterprise networking infrastructure, including routers and switches. He also writes The Cisco Connection blog and can be reached on Twitter @Jim_Duffy and at

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