24 May 2024

Software defined networking (Image by OCTOBITS)

Octobits Blog – Software defined networking (SDN) emerged to transform how networks are designed, deployed, and managed.

It’s common knowledge that computer networks had a certain way they worked for years before.

Networking hardware, like switches, routers, etc., came with their own operating systems and ways of doing things.

Network administrators worked within those fixed systems. It was complex, and changes were often slow and challenging.

And yes, SDN has redefined network architecture by introducing flexibility and control previously unattainable with traditional networking methods.

Now, we’ll break down the essentials of software-defined networking to understand how it can be a powerful tool for your company.

What is Software-Defined Networking (SDN)?

Software-Defined Networking (SDN) is an approach to network virtualization where open interfaces allow the network administrator to programmatically initialize, control, modify, and dynamically manage network behavior and provide an abstraction of lower-level functionality.

In traditional networking, each device, like a switch or router, has its own control plane (the ‘brain’ that decides how to handle the traffic) and data plane (the part that does the actual forwarding of data).

SDN changes this with a centralized approach. The central idea of SDN is to separate the control plane from the data plane.

The main idea of SDN is to enhance network management by offering a more adaptable and efficient method.

So, SDN enables the ability to make adjustments and improvements that were difficult to implement dynamically before.

SDN creates a central command center for the network. This command center takes the decision-making power (the control plane) out of individual devices and houses it in a software-based SDN controller.

Meanwhile, the actual switches and routers (the data plane) become simpler, focusing purely on forwarding data as instructed by the controller.

To make this possible, the SDN controller needs a way to communicate with the network devices.

APIs (Application Programming Interfaces) play a vital role in that interaction. SDN uses southbound APIs, such as OpenFlow, as a standardized language of instructions.

The controller uses these APIs to tell the network devices precisely how to handle traffic, creating a clear chain of command.

This SDN model shifts the focus from managing individual devices to orchestrating the network as a whole. 

This transformation can translate into greater efficiency, faster responses to change, enhanced security, and the ability to drive innovation within your organization.

As an example, you can simplify the network troubleshooting process; more efficient, less time-consuming, and less cost-savings.

You can get the details of network troubleshooting in our report How Network Troubleshooting Made Easy IT System: Step-by-Step Guide‘ to gain insight into how to improve the process.

Components of SDN

In SDN, the architecture consists of three distinct layers; application, control, and infrastructure, which interact through APIs for dynamic management.

The application layer is the realm of SDN applications. These applications address specific network needs.

These applications focus on streamlining network configuration, tightening security, or gathering in-depth data about network performance.

These applications operate above the SDN Controller—this central unit translates high-level objectives into device instructions.

Then, we have the SDN controller, the true heart of the system. The controller has a bird’s-eye view of the entire network.

The controller understands how all the devices are connected. Its key job is to take the requests from the applications above (like “create a secure communication path”) and translate them into precise instructions for the network devices below.

To communicate these instructions, the controller relies on southbound APIs like OpenFlow. Yup, between applications and controllers, there are communication aspects. 

These APIs create a standardized language for the controller to tell the network devices exactly how to handle data traffic.

Then, we have the network devices, like switches, routers, etc., to execute the instructions.

These network devices lose some of their traditional decision-making ability in the SDN framework.

Instead, the network devices focus on carrying out the instructions sent from the controller.

Finally, northbound APIs connect the controller back to the applications, allowing the applications to send requirements down and receive information on the network’s status.

This creates a continuous loop where applications outline the desired state of the network, the controller devises the plan, and the devices below execute it.

Benefits of Software-Defined Networking

In traditional networks, making even a small change often means configuring multiple devices individually. This can be time-consuming.

With SDN,  you change the central controller, which can automatically update the instructions sent to the whole network.

For your note, kindly check how change control management is in more detail atChange Control Guideline: The Secret to Stress-Free IT Updates.’

The SDN controller also gives you a complete, real-time view of the entire network, including how devices are connected and traffic flows.

Instead of having to piece together information from separate devices, you have a centralized dashboard providing greater control and simplifying troubleshooting.

One of the most potent aspects of SDN is the ability to control network behavior through software.

This network as a software model allows you to customize the network to your specific needs.

This approach makes implementing new features or services far easier and faster compared to a traditional network environment.

With all those advantages, SDN makes the network more adaptable and easier to customize. It means there are new possibilities with SDN.

You can quickly test and roll out new technologies or adjust the network to support new applications – giving your business an edge.

In business, it means potential cost savings. While not a guaranteed outcome, SDN potentially reduces costs.

But simpler network devices, centralized management, and greater network efficiency can all contribute to reducing operating expenses over time.

What is an Example of SDN?

SDN separates a network’s control and data planes, enabling centralized management and dynamic resource allocation.

This separation allows for direct programmability of the network, making it more responsive to changing business needs.

SDN facilitates greater network visibility, scalability, and security while being open-source and vendor-neutral, thus offering a flexible and cost-effective networking solution​​.

We can see those advantages in the ServiceNow shifting program. ServiceNow, a digital workflow company, embarked on a network automation journey to support its business transformation.

ServiceNow partnered with Juniper to migrate its network to a next-generation solution that includes wired, wireless, and SD-WAN technologies.

This move resulted in a 60% cost avoidance in network CapEx/OpEx spending and a 50% reduction in network deployment times, highlighting the operational efficiencies and cost savings that can be achieved with SDN​.

Then, we also see BT Group’s network cloud initiative as another SDN shifting example.

BT Group implemented SDN to create a highly scalable and robust cloud core. This core network is designed to support the diverse needs of their broadband, mobile, and other critical network applications.

This network cloud has scaled to accommodate tens of millions of users without significantly increasing staffing numbers, demonstrating SDN’s potential to streamline operations and reduce environmental impact.

The project successfully migrated millions of mobile subscribers to a private cloud, showcasing SDN’s scalability and operational efficiency​.

SDN Deployment Models

The beauty of SDN is its flexibility. There isn’t a single, -size-fits-all way to deploy it.

The best model for your organization will depend on your specific needs, existing infrastructure, and where you want to focus your control.

On-Premises SDN

The entire SDN setup in this model – the controller, applications, etc. – lives within your data center.

This model offers complete control over the network’s operation, security, and management, making it suitable for organizations with strict regulatory compliance requirements or those that handle sensitive data.

It allows your IT teams to rapidly provision, configure, and manage network resources with high visibility and control over the network traffic and policies.

Cloud-based SDN

Here, the SDN controller runs in a cloud environment. This model is advantageous for organizations looking to leverage the scalability and flexibility of cloud resources.

It simplifies management by abstracting the underlying complexity of network configurations. It also enables seamless control over cloud-resident and on-premises network resources.

This approach is particularly appealing for businesses focusing on cloud-first strategies, offering them a unified way to manage hybrid or multi-cloud environments.

Hybrid SDN

This approach offers the best of both worlds–you maintain some SDN components on-premises while leveraging the controller or specific applications in the cloud.

You can maintain sensitive workloads on-premises for security and compliance while utilizing cloud resources for scalability and cost-efficiency.

This model supports dynamic workloads and can be particularly useful for companies transitioning to the cloud.

Because this allows companies to scale their network infrastructure at a pace that suits their evolving business needs.


SD-WAN (Software-Defined Wide Area Network) is a specialized application of SDN focused on connecting geographically dispersed sites (like branch offices) back to a central location.

This SDN improves bandwidth utilization, reduces network congestion, and enhances overall network performance.

By applying SDN’s flexibility and intelligence to WAN connections, you can achieve more efficient routing, application-aware traffic management, and improved resilience without the complexity traditionally associated with managing WAN connections.


Software-Defined Networking represents a paradigm shift in how networks are designed, operated, and managed.

Its benefits, from enhanced efficiency and security to greater agility and flexibility, underscore its pivotal role in the future of networking.

As technology continues to advance, the principles of SDN will become increasingly integral to the development of resilient, adaptive, and secure network infrastructures.

If you’re just beginning to explore SDN, the journey toward software-defined networking can transform your company network.

Even if you have existing Software-Defined Networking (SDN) knowledge, there are always opportunities to deepen your understanding and find new ways to apply it for more significant benefits.