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Network World - Cisco, Brocade, Dell among others have jumped on board and look to ride the wave that is software defined networking. This despite experts' assertions that SDNs threaten Cisco's dominance in the tech industry.
As is somewhat typical of emerging technologies, there isn’t a universally agreed to definition of what is meant by software defined networking (SDN). Over the last year or two most of the definitions have focused on the decoupling of the network control plane from the network forwarding plane.
The definition of SDN that is currently emerging focuses somewhat less on decoupling and more on providing programmatic interfaces into network equipment, whether or not there is a separation of the control and forwarding planes. A minor reason for this shift in focus is because Cisco recently announced that as part of its SDN offerings, it will provide APIs into multiple platforms that they provide.
This is not a Cisco-only approach, as other vendors; including Arista, Extreme and Juniper currently provide direct access to their products. One advantage of this approach is that it enables very detailed access into, and control over, network elements. This approach, however, doesn’t provide a central point of control and is vendor specific. While some network service providers may adopt this approach in the near term, it is unlikely to gain much traction in the enterprise market for the foreseeable future.
With the more common definition of an SDN, global control of the network is achieved by the logical centralization of the control plane function, and the network operations organization can deal with a pool of network devices as a single entity. With an SDN, network flows are controlled at the level of the global network abstraction, rather than at the level of the individual devices, usually, but not always, with the aid of the OpenFlow protocol.
The group most associated with the development of a standards based SDN is the Open Networking Foundation (ONF). The ONF was launched in 2011 and has as its vision to make OpenFlow-based SDN the new norm for networks. To help achieve that vision, the ONF has taken on the responsibility to drive the standardization of the OpenFlow protocol
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.
There is no doubt that SDN can potentially provide very significant value to IT organizations. There is also no doubt that in the current environment SDN is only appropriate for early adopters. Given the immaturity of the current products, standards and APIs, any IT organization that is looking to implement SDN in the near term should only do so in a somewhat limited manner, such as implementing SDN for a very specific use case. In addition, given the embryonic state of the market, the interoperability of products that claim to support the same SDN related standards cannot be assumed so IT organizations should only work with vendors that have demonstrated a high level of interoperability.