What is Software-Defined Networking (SDN)?

Software-defined networking (SDN) describes an architecture that separates the network control plane and the forwarding plane, aiming to simplify and improve network control. IT teams are more able to rapidly adapt to changing business requirements and application needs.

SDN is a highly flexible, agile way to adapt to growing bandwidth requirements. By separating the network control and forwarding planes, SDN makes network control a programmable entity and abstracts the infrastructure underneath.

Network engineers benefit from SDN because they no longer have to wrangle individual sections of the network to shape traffic. Instead, SDN takes care of this task, directing these individual “switches” to provide services when the business requires them.

What is Software-Defined Networking (SDN)?

Features of software-defined networking

There are 5 unique, defining features of software-defined networking:

1. Engineers are able to directly program network control.

2. As business and application needs change, administrators can adjust and redirect the flow of network traffic.

3. SDN controllers contain network intelligence, which provides a holistic view of the network through a central switch.

4. Network managers can configure network resources quickly and easily through automated SDN services. They also have the freedom to create these SDN programs themselves since no proprietary software is needed.

5. SDN is based on and implemented via open standards. As a result, SDN streamlines network design and eliminates the need for vendor-provided, proprietary devices.

Architecture of software-defined networking

In a nutshell, software-defined networking relies on open APIs to create a central “switch” that allows administrators and managers to decide and program network behavior. SDN unhatches otherwise closed networks, allowing IT teams to manage their network, applications, and devices consistently and through a single point of control. 

Software-defined networking performs various tasks and encompasses various technologies. But its original, most defining purpose was to separate the network the data and network control plane. The control plane is the “brains” of the operation, deciding how and where packets should move throughout the network. The data plane is the transport system, moving these packets according to the control plane’s directions.

The process of splitting up these two planes is called disaggregation. In a traditional network environment, networks are aware of the applications running throughout the system; in a software-defined network, the applications are granted information about the network, creating a two-way street of information.


There are three components that make up software-defined networking:

  1. First, we have SDN applications. These applications relay actions and request resources through the SDN controller using APIs. SDN applications can assume various forms and serve various functions, such as managing the network, providing analytics, or even running datacenters;
  2. Second, and perhaps most importantly, is the SDN controller. SDN applications send instructions to the SDN controller, which then relays that information to networking components. The SDN controller is also responsible for collecting network information from hardware, delivering this information and relevant statistics back to the applications;
  3. The third component is a system of SDN networking devices. In the network, these devices are responsible for forwarding and data processing tasks, both of which can be performed for the data path as well.

Benefits of software-defined networking

Off the bat, businesses investing in SDN are likely lured in by its ability to support data-heavy applications. But beyond that purpose, there are innumerable benefits that make SDN a worthy venture. Below are several of the top advantages.


In a software-defined network, users can view the entire network through a centralized source, which simplifies provisioning and managing processes. 

Business demands vary day-to-day, so IT managers need to set up “what if” network configurations to accommodate demands from new applications and virtual machines (VMs). In a software-defined network, these “what if” configurations are easy to do and pose no impact on the network. 

Improved security makes SDN a no-brainer for many businesses. In a software-defined network, security is centralized. In this central controller, an IT manager can create and distribute security policies throughout the enterprise with ease. 

Lower operating expenses is another alluring benefit of SDN. Because a software-defined network improves resource and server utilization overall, businesses will experience reduced operational costs, administrative expenses, and more.

In addition to reduced operating expenses, choosing a software-defined network lets businesses commoditize their hardware, repurposing it via a central SDN controller. Businesses can also deploy and leverage more affordable hardware through the same intelligent central switch.

SDN is an excellent way to help “cloudify” the datacenter, ultimately helping to unify the components of a business’s infrastructure. Specifically, a business can abstract, and therefore unify, their cloud resources through SDN. 

As mentioned in an earlier section, the ability to redirect and shape data traffic is a defining feature of SDN. This enables IT teams to improve their service delivery, network responsiveness, and more, which makes the end user experience more seamless.

Software-defined networking and security

There are different levels of security protection offered via software-defined networking. Perhaps most notable is the centralized intelligence SDN offers, enabling IT administrators to quickly and easily set and keep security policies. From there, these policies can be universally enforced  throughout the network, and they can be maintained and enforced through central control. 

Furthermore, SDN creates an abstraction layer between the software and the hardware, allowing IT teams to bypass proprietary devices and simply start developing security tools to implement across the network. As a result, there is greater transparency for gathering insights and possible threats in the event a security breach occurs. 

Ultimately, security is scalable with SDN. Rather than necessitating expensive, proprietary hardware and security controls, IT teams can create, control, and deploy security policies at scale as software grows, new clouds and applications are provisioned, or as business needs change. Not to mention, should a segment shut down or create a security gap, the transparency of SDN allows administrators to quickly and easily detect malware. 

How is software-defined networking used?

There are multiple use cases where SDN would be beneficial. First, SDN can help support DevOps initiatives. Application updates, deployments, and even IT infrastructure components can all be automated through SDN, all of which can occur as DevOps applications and platforms are created and deployed. 

Second, businesses can leverage SDN controllers to improve the functionality of campus networks, which are often complex due to ongoing WiFi and Ethernet needs. The central SDN controller “switch” delivers automation and centralized management, ultimately improving security and helping businesses develier more high-quality services in their network.

Third, service provider networks can leverage SDN to automate the process of provisioning networks for improved service management and increased control.

Finally, businesses can enjoy the increased protection and simplified firewall administration that SDN provides. Companies can create distributed firewall systems through the virtualization capabilities of SDN, delivering an extra layer of security to prevent a breach from hopping from one VM to another. Not to mention, administrators and managers can centrally track and change network activity to detect and eliminate breaches before they strike.

Related resources

Modernizing Your Datacenter: A Security-First Approach

Application-Centric Security

Big Switch + Nutanix: Ideal SDN Fabric for Hyper-Converged Infrastructure

Cisco ACI with Nutanix

Nutanix Flow Delivers Software-Defined Networking to Secure Applications with a Single Click

Learn more about software-defined networking

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