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What Is Software Defined Networking: A Complete Explanation

Wondering about software-defined networking? We discuss software-defined networking, explain how it differs from traditional networks, and outline its benefits.

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What Is Software-Defined Networking?

Software-defined networking is an architecture that uses software to abstract layers of a network to make networks more flexible.

SDN is a popular choice among enterprise networks as it allows an organization to centralize its control over network behavior. This makes scaling applications, controlling network resources, and managing traffic much easier for larger networks.

As cloud computing and virtualization become more common, so does SDN architecture. SDN makes it easier to control traffic across multiple applications and networks from a single place. Administrators can set NAT policies, configure firewall rules, and modify quality of service from one place rather than balancing settings across different platforms.

Software-Defined Networking vs. Traditional Networking

The main difference between software-defined networking and traditional networking is that SDN uses software and application programming instead of using physical routers and switches to control traffic.

Both networks have a control plane and data plane. The control plane dictates how packets are forwarded. Routing tables are a simple example of a control plane. The data plane listens for instructions from the control plane and routes the traffic.

In a traditional network, the data plane and control plane are fixed and controlled by firmware inside physical routers and switches. This means traffic relies on this hardware to move throughout the network. 

This traditional model makes network management difficult, especially at a larger scale. Traditional networks have distributed control, meaning administrators have to change configurations and network setting across multiple devices to achieve specific QoS. As you can imagine, in an enterprise network this can make creating consistent network conditions very difficult.

In a software-defined network, the data and control planes are decoupled. Instead of network hardware, software is used to route traffic and control network resources. This makes it easier for administrators to set policies and control traffic across an organization. It can also reduce the amount of hardware needed to achieve certain network goals.

Software-defined networks have the following characteristics:

  • Programmable network functionality
  • Automatic configuration
  • Application-aware QoS
  • Uses software rather than hardware to route traffic
  • Centralized control

Components of a Software-Defined Network

There are four primary components of a software-defined network:

SDN Controllers

SDN controllers work with applications to determine the destination of network traffic. You can think of the SDN controller as the brain of the operation. These controllers can act as load balancers and places where administrators can control the traffic. The controller typically runs on a server and uses protocols such as OpenFlow to tell switches where to send traffic.


The application communicates information about the network and requests. These applications send data regarding resource availability, network allocation, and specific data packet behavior.

Network Devices

These are the devices that receive instructions from the controllers. In most cases, these are switches, repeaters, and routers.


As mentioned earlier, SDN relies on software programming to control traffic. OpenFlow is an open-source programming language used to control traffic across the SDN.

Models of Software-Defined Networking

Administrators can implement SDN in a few different ways to suit their needs. Below are a few models commonly found across different environments.

  • Open SDN - Uses open-source protocols like OpenFlow to control traffic at the data plane level.
  • Hybrid SDN - Combines SDN with traditional networking protocols in the same environment. This model is typically used when migrating from traditional to SDN architecture.
  • SDN via API - Data is controlled via API rather than by network protocol.
  • SDN Overlay - Overlays a virtual network on a hardware infrastructure that allocates resources across different channels. This method leaves the physical network untouched.

Advantages of Using SDN

With environments becoming more complex, the demand for unified traffic control and management solutions grows each day. Below are a few benefits that software-defined networks can bring to an organization.


SDN leverages open-source protocols and hardware to achieve a high level of customization. This allows organizations to automate provisioning and maintenance tasks as well as implement self-healing routes that immediately provide dynamic failover in the event of a hardware failure.


SDN provides a unified view of an organization's entire network, making it easier for management and provisioning. Enterprise environments can reduce their complexity and deploy networks faster using an SDN. Administrators can improve service delivery and provide more flexibility during provisioning across both physical and virtual network devices from a single location.

This centralization allows administrators to manage configurations and traffic flow more efficiently in ways not possible across managed routers and switches. Applications can be written to control traffic across the SDN without impacting the physical network infrastructure.


SDN saves time and reduces complexity, which can decrease outages down the line. While SDN controllers do cost money, many environments will see cost savings when compared to a traditional network solution. Businesses often experience lower OPEX costs with SDN due to improved efficiency and management.


Centralized management in SDN makes administration easier and allows admins to create and modify security policies uniformly across the enterprise. In a traditional network, this might require changing policies across multiple hardware devices for a single user, whereas in SDN, a single update can make these changes automatically.

The Celona Solution

Celona’s 5G LAN architecture leverages software-defined networking principles to provide network orchestration to simplify and accelerate deployment of private 5G technology across enterprise networks.

In our journey to make implementing private mobile networks an out-of-box experience, in a Celona network, onboarding can be done alongside existing wireless and IT infrastructure, without interrupting business operations.

If you’re building your network for the future, Celona can help. Check out our network planner to see what your network would look like on the private cellular spectrum, or test-drive the Celona Solution for yourself through our free trial.

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