What is Software Defined Networking (SDN)? The Future of SDN

Businesses, carriers, and other enterprises are continuously facing onslaughts from multiple sources. Multimedia content continues to grow exponentially, cloud computing is at an all-time high, and mobile usage is higher than ever.

Additionally, there is pressure for organizations to cut their costs while not compromising on their revenue. When all these forces converge, they pose a serious threat to the traditional business model.

In a bid to adapt, many companies are turning to SDN technology to change the way they go about network monitoring operations and designs to increase their efficiency.

SDN allows you to program network behavior by utilizing software applications that use open APIs in a centrally controlled manner. When you open up the network platforms which are conventionally closed and implement a central SDN control layer, one can manage entire networks and their devices without regard to how complicated the underlying network technology is. This brings us to the question; what is software-defined networking?

What is Software-Defined Networking (SDN)?

The software-defined networking definition can be derived from the function of SDN. As such, software-defined networking SDN is a means of managing networks. It does this by separating the forwarding plane from the control plane. Thus, SDN is an approach that complements network functions virtualization (NFV) through network management. And even though both do manage networks, they use entirely different methods.

Software-defined networking provides you with a centralized point of view of the network. This will allow you to act as the network’s brains. Thus, an SDN Controller is able to relay information to the applications using northbound APIs, and to the routers and switches using southbound APIs.

Therefore, the programmable and centralized SDN environments are able to adapt to your organization’s rapidly changing needs easily. This way, SDN limits wasteful  User Account Provisioning and enhances network innovation and flexibility. This is what will lower your costs of doing business.

The Origin of SDN

Somewhere around the mid 90’s, Sun Microsystems launched Java, and it was the first time the concept of SDN was realized. Geoplex, an AT&T Labs project, was created to be a service platform that managed online networks and services. At the time, it was regarded as a ‘soft switch’ which delivered the services of reconfiguring network traffic and balancing the workloads.

An engineer from Sun Microsystems, in 1998, launched WebSprocket with the desire to produce an object-oriented network operating system. This instigated the launch of VMServer and VMFoundry in 2000 to enable the birth of custom services that could be launched over a network. 2001 saw Ericsson and WebSprocket coming together to design the first soft switch which was commercially available. Nevertheless, it didn’t last long.

The concept was still under review and construction for a while until 2011 when the Open Networking Foundation was created to vouch for the use of SDN. The particular one being promoted was OpenFlow; a standardized communications interface protocol.

The Concept of SDN

Software-defined networking aims to provide companies with stable but adaptable Sdn architectures that are able to handle the complex systems which are a mix of cloud and in-house infrastructure. SDN achieves this by manipulating the underlying network infrastructure to separate forwarding functions and network control. As such, network control becomes programmable and can be manipulated using the software.

The implication is that greater agility is realized, and the network administrator can dynamically adjust the flow of traffic across the network depending on the need.

How SDN Works

Software-Defined Networking (SDN) operates by separating the network architecture into three distinct but interconnected logical layers: the application layer, the control layer, and the infrastructure layer. These layers communicate with each other through API’s, enabling centralized control, flexibility, and automation in managing network resources.

1. Application Layer

The application layer sits at the top of the SDN architecture and consists of various networking applications and business-driven services. This layer is where organizations define how the network should operate based on operational needs, such as performance, security, bandwidth allocation, and routing preferences. Instead of relying on traditional hardware-based solutions such as dedicated firewalls or load balancers, SDN enables these functions to be implemented as software applications. These applications communicate their requirements directly to the control layer, ensuring that network behavior aligns closely with business objectives.

2. Control Layer

The control layer is often referred to as the “brain” of the SDN system because it makes all key decisions about network traffic. Managed by the SDN controller, this layer receives instructions from the application layer and translates them into actionable network policies. It determines how data should flow across the network, allocates resources efficiently, and enforces security and performance rules. One of its most important functions is maintaining a centralized view of the entire network, enabling smarter decision-making and simpler network management than in traditional decentralized systems.

3. Infrastructure Layer

The infrastructure layer forms the foundation of the SDN architecture and comprises physical and virtual networking devices, such as routers, switches, and access points. This layer is responsible for the actual movement of data packets across the network. It does not make decisions on its own; instead, it executes instructions received from the control layer. By focusing solely on forwarding and transmitting data, the infrastructure layer ensures efficient and reliable communication between devices while relying on higher layers for policy and control decisions.

Types of SDN

Managed Service Providers can implement Software Defined Networking (SDN) in different ways depending on how control is exercised over the network and how it integrates with existing infrastructure. Broadly, there are four main types of SDN models: Open SDN, API-based SDN, Overlay Model SDN, and Hybrid SDN. Each approach offers a different balance of control, flexibility, and deployment complexity.

1. Open SDN

Open SDN is built around the idea of using open standards and protocols to manage both physical and virtual networking devices. In this model, network behavior control is separated from the hardware and handled through open communication protocols. This makes it easier for different vendors, developers, and network teams to collaborate and innovate without being locked into proprietary systems. Open SDN is often preferred in environments that value flexibility and community-driven development.

2. API-Based SDN (Application Programming Interface SDN)

In API-driven SDN, network control is achieved through software interfaces that enable applications and orchestration tools to communicate directly with network devices. These APIs act as a bridge between the SDN controller and the infrastructure, enabling automation of traffic management, configuration, and policy enforcement. This approach is widely used in cloud environments where integration with management platforms and applications is essential for scalability and automation.

3. Overlay Model SDN

The Overlay SDN model creates virtual networks on top of existing physical infrastructure. Instead of replacing traditional hardware, it builds an additional abstraction layer using tunneling techniques. This allows multiple virtual networks to run independently over the same physical network. It is especially useful in data centers and hybrid cloud setups where organizations need to connect on-premises systems with remote cloud environments while maintaining isolation and flexibility.

4. Hybrid SDN

Hybrid SDN combines traditional networking methods with SDN-based control mechanisms. In this model, both conventional routing protocols and SDN controllers operate in parallel, enabling organizations to gradually transition to SDN without fully replacing existing infrastructure. It intelligently assigns traffic handling based on performance, policy, or application requirements. This makes it a practical choice for enterprises that want to modernize their networks incrementally while maintaining stability in legacy systems.

SDN vs. Traditional Networking

Traditional networking and Software-Defined Networking (SDN) represent two different approaches to managing and operating networks. While traditional networking relies on hardware-based, device-level control, SDN introduces a more modern, software-driven model with centralized control and automation. This shift significantly improves flexibility, scalability, and efficiency in network design and management.

Feature	Traditional Networking	Software-Defined Networking (SDN)
Architecture	Control and data functions are integrated into each device (routers and switches).	The control plane is separated from the data plane with centralized control.
Control Mechanism	Distributed control, where each device makes its own decisions.	Centralized control managed by an SDN controller.
Management	Device-by-device manual configuration is required.	Centralized, software-based management of the entire network.
Configuration Changes	Slow and complex, it requires manual updates on multiple devices.	Fast and automated through software-defined policies.
Scalability	Limited and hardware-dependent; scaling requires new devices.	Highly scalable with minimal hardware dependency.
Flexibility	Less flexible due to rigid hardware configurations.	Highly flexible and adaptable to changing network needs.
Automation	Minimal automation relies heavily on manual intervention.	High-level automation for traffic management and provisioning.
Traffic Management	Static routing and predefined paths.	The controller dynamically optimizes routing in real time.
Cost Efficiency	Higher operational costs due to hardware and manual effort.	Lower operational costs through centralized control and automation.
Suitability	Best for traditional enterprise networks with stable requirements.	Ideal for cloud environments, data centers, and modern agile networks.

Benefits of Software Defined Networking

• Over the past decade, traffic patterns in business have undergone dramatic changes due to the heightened use of mobile devices. This has called for more and more systems to be moved to the cloud. Therefore, when Ethernet switches could facilitate the traditional and simple client-server designs, they can no longer cut it as what is needed now is a system that offers dynamic flexibility.
• Thus, one of the primary advantages of software-defined marketing is the ease at which it provides access to private and public cloud services. Hence, your business will easily access these services as well as dictate how, where, and when it wants to. This allows for simpler and faster scaling of resources to meet any changes in demand.
• Also, remember that IT is becoming increasingly consumer-led. People have a preference for using their mobile devices to access data and networks. Thus, using SDN, your IT department shall facilitate this access leading to better consumer satisfaction.
• Among the benefits of software-defined networking, handling big data must be where this technology really states its case. Large volumes of information or data require many utilities such as multiple virtual machines and servers to enable parallel processing. This would call for a massive investment if you are still utilizing conventional networking. With SDN, however, these processes will be handled much faster and at a much lesser cost.

The Future of SDN

This post has discussed SDN mainly in regard to business networks. However, there are sectors where SDN can be utilized with good effects and we are likely to realize these benefits in the coming years.

For instance, software-defined mobile networking (SDMN) shall enable the design and protocol of mobile networks to be controlled by software. The implication is that service providers shall offer networks at lower costs through utilizing commodity hardware.

Another sector will be Managed SD-WAN (Software definition for wide area networks). The benefit of utilizing sd wan is that it will significantly cut costs by halting the use of costly leased lines and managing networks using internet connections instead.

Nevertheless, since SDN is open source, concerns about its security are not far-fetched. This is because this characteristic is what makes it vulnerable to attacks from hackers and disrupting the network. Even though these are legitimate worries, SDN is still easier to defend due to its centralized network monitoring system.

Additionally, the centralized control system is a concern too. For instance, if this control falls into the wrong hands, the consequences could be disastrous. Also, even if the administrator is trustworthy, if they are not well trained and consequently mess up the configuration, the network would become hugely impacted.

Also remember that even while SDN is cited as a tool that allows for easier transition to cloud technology, the cloud itself is a relatively new tool. Thus, for a company to incorporate these technological changes, it must enlist the services of a professional who has the necessary skill set and experience to handle the transition as well as manage operations smoothly.

As the world turns towards virtualized systems, SD-WAN use is going to become more common, and ultimately, a must-have. Thus, ensure that you do not join the party late.

ExterNetworks is a managed service provider that offers cloud and software solutions to businesses looking to make a transition to virtualization. Our company has immense experience in cloud-based solutions and has helped numerous companies to cut on costs and increase their ROI through our managed services. When you sign up with us, we shall assume control of your business network and manage its traffic more effectively so that it can yield more returns. To learn more about our managed services, visit us here.