What SDN is and where it's going

What SDN is and where it's goingForrester analyst Andre Kindness says a lot of clients ask him how they should think about software-defined networking (SDN), which has been heralded for years as the next great thing in the industry.

SDN – which is an architecture approach, not a specific product - has traditionally been thought of as virtualizing data center networks. This typically means separating the management of the control plane of network devices from the underlying data plane that forwards network traffic. Using a software-defined system to control this disaggregation brings many benefits, including increased network management flexibility and being able to more easily implement fine-grained security policies.

But Kindness says too often network operators think about SDN with too narrow a focus. There’s been an evolution in the SDN market in recent years, driven by increased demands on the network. To meet these new challenges the underlying technology that powers SDN has been applied to other areas of networking. “The network in the data center isn’t an isolated domain,” Kindness explained. “How does it interact with public cloud, how are branch offices being connected to, what does the world of IoT mean for the network? It’s all part of this new modern network.”

Current snapshot

SDN emerged in the early 2010s out of necessity, according to IDC networking analysts Rohit Mehra and Brad Casemore. Many networks of today were designed for client-server applications running on non-virtualized infrastructure. “Virtualization, cloud, mobility, and now the internet of things (IoT) have exposed the limitations of traditional network architectures and operational models,” Mehra and Casemore wrote in their SDN Forecast published in 2016. “By now, SDN has advanced beyond its adolescence and early euphoria and has settled into early adulthood as something of a known commodity. It's not so much the next big thing on the networking horizon as much as it is a reality and inevitability for enterprises and service providers worldwide, even for those who've yet to embrace it.”

VMware’s 2013 purchase of Nicira was considered a seminal moment in the SDN industry and launched the virtualization giant into becoming a networking vendor. Today, VMware’s NSX SDN product is based off that technology. Cisco’s Application Centric Infrastructure is the basis for its SDN offering. Many other companies, such as Juniper and Arista have their own SDN offerings too.

IDC estimates the SDN market has grown from a $406 million industry in 2013 to more than a $6.6 billion market in 2017. IDC predicts the SDN market will continue to grow at a 25.4% compound annual growth rate to $13.8 billion by 2021. IDC estimates that SDN is emerging out of the early adopter and into the early mainstream stage of its development.