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Sorting out SDN, NFV, Network Virtualization and the New Networking

Written By: Stuart Miniman


A lot has changed in a year. Soon after I wrote Networking Revolution: Software Defined Networking and Network Virtualization, Nicira was purchased by VMware for more than $1B. For many outside of the networking world, this gave instant credibility to the SDN (Software Defined Networking) movement.

This increased scrutiny has not necessarily clarified what truly defines this new wave of networking. Networking has always been a complicated environment filled with numerous protocols and arcane terminology. SDN, NFV (Network Functions Virtualization), and network virtualization are three different solutions (with some overlapping terminology) that look to bring a new generation of networking to market. All of these solutions aim to bring networking into a more automated and scalable era geared for virtualized and cloud environments.

Ivan Pepelnjak (see the full interview) compared SDN and network virtualization to changes seen in the past with telephone service. In the current state of networking, a virtualization administrator needs to call the networking administrator to set up VLANs. This is similar to the rotary days of telephone where the operator had to manually patch a call through. Ivan’s analogy is that SDN will bring networking into the today’s telephone world while network virtualization is looking to skip straight to Skype.


SDN is the idea of decoupling the forwarding of the physical switch from the control plane and the topology calculation. Configurations are not done at the single switch level; they can now be done for a group (today up to 50 switches) at the same time.

SDN is deployed today in some of the largest networking environments such as service providers and Web companies. See Brent Salisbury’s look inside how Google has been using SDN for the last two years. Today, the term “SDN” is as vague and misused as “cloud” was five years ago. Software is not new to networking, and therefore many existing software solutions are being rebranded with “SDN-washing”.

Under the SDN umbrella are a number of tools. OpenFlow is a “low level screwdriver” in the SDN toolbox. The launch of the OpenDaylight Project, has signaled a concerted effort to standardize on an open source controller. The value of the controller is as an enabler for applications and broker for hardware.


See the interview with Brocade’s PG Mennon for the discussion of SDN and NFV

SDN is primarily at the packet forwarding level. NFV is the ability to take more computationally intensive services (such as firewalls and load balancing) and run them as software that could run in a virtual machine on commodity hardware. Virtual routing is one of these services; Brocade’s Vyatta vRouter product is a shipping example of NFV. See Network Function Virtualization or NFV Explained for more on the definition and standards for NFV.

Network Virtualization

Network virtualization is a compelling vision that was put forth by Nicira. Now as part of VMware Nicira has an even greater opportunity to span between physical and virtual networking. In a recent article, VMware’s Brad Hedlund reinforces the relationship of server and network virtualization. He states that the primary goal of network virtualization is to decouple physical and virtual resources, which allows the network to be as flexible as and work in lock-step with virtualized compute. I would say that while network virtualization is it’s own use case, it does overlap slightly with both the SDN and NFV definitions.

Commodity hardware and SDN

Interview with Greg Scherer of Broadcom, whose merchant silicon spans from enterprise to commodity switches

A financial analyst recently told me that he heard that SDN solutions were 1/3 the cost of existing networking solutions, and this is why VMware bought Nicira. It is a common misconception that SDN means a great reduction in cost through either consolidation (such as what server virtualization drove) and/or commodity hardware. The reality is that neither SDN or network virtualization immediately change the infrastructure requirements for networking – there is no decrease in ports. Some of the largest Web companies have moved to commodity switches, but this move is orthogonal to SDN.

Hyperscale companies have a very different management model than the enterprise. The Facebooks and Googles of the world will spend significant coding and architectural time to create solutions that can save them money when they are spending more than $1B on infrastructure. Enterprise IT does not buy on the same scale and does not have the same programming and architectural knowledge, so it will spend money on solutions to save time. (See Tom Hollingsworth’s article Why Facebook’s Open Compute Switches Don’t Matter to You) A number of startups including Plexxi, Pica8 and Cumulus Networks are creating solutions to bring commodity switches to the enterprise.

Action Item: The networking industry needs to move beyond today’s world of manual configuration and embrace automated solutions that are coordinated with the rest of the (virtual) infrastructure. Network administrators are urged to help spur this transition to avoid being left behind with outdated skills. SDN, NFV and network virtualization each have their place at delivering new solutions to the market.

Footnotes: Also see my video on SDN washing and the slow rate of adoption in the networking industry and read about how SDN, OpenFlow and OpenStack Quantum compare.

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