What Is Software Defined Networking and Why Should We Care?

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Dan Omalley

Expert in 5G
What is software defined Networking

SDN is a unique networking architecture approach. We can control and manage networks through software applications in this architecture. Hence, it separates the data plane from the control plane. This is the primary idea. Throughout this blog, I will explain “what is software defined networking (SDN)?” and how it works.

This relatively new technology has already impacted the networking industry. Its concept was first introduced in the early 2000s. Since then, many vendors (including Nybsys) have adopted SDN in networking.

Traditional networks are often complex and inflexible. It makes them less quick and makes it easier to make any changes. In this background, SDN appeared as a more flexible and agile solution to fulfill business needs in this ultra-modern age. Thus, I suggest you read the whole post to learn about software-defined networking.

The framework of SDN architecture is a shift from traditional networks (hardware-centric) to software-driven networks. This shift was inevitable due to the increasing need for flexibility, scalability, and efficiency in networking. Besides, the architecture enables programmable control of the network, unlinking network architecture components, and enhancing interoperability and openness.

Components of SDN Architecture

You may think about what makes the software-defined networking architecture. Well, it has several components:

SDN Applications

You need software applications to make the network work in this architecture. These apps relay requests or networks through the SDN Controller using APIs. 

SDN Controller

Call it the brain of SDN architecture. It decides how traffic should flow through the network (from hardware to applications). Also, it communicates with network devices using APIs. In this way, it enables centralized management, automation, and policy enforcement across the network.

Southbound APIs

Consider these APIs as the language of the controller. These interfaces enable communication between the SDN controller and the underlying network devices, like switches and routers. Hence, some popular protocols are OpenFlow, NETCONF, and BGP. 

Northbound APIs

 Like the language, these APIs are doors and windows through which other systems can access and interact with the SDN controller. However, these APIs enable interaction between external apps and the SDN controller. You can integrate SDN with other IT systems using these APIs.

Network Devices

 In an SDN environment, network devices like switches and routers become programmable forwarding elements. They execute the instructions received from the controller via southbound APIs. Then, they push data packets along the designated paths. In short, these devices make data processing and forwarding simple. 

How the SDN Architecture Works

In a traditional network, each switch has its data and control planes. In SDN, the control plane is removed from the switch and assigned to a centralized unit called the SDN controller.

Hence, I have already given you a hint of how the SDN architecture functions. These functions are conducted in these ways:

Policy Configuration

Network administrators define policies through the northbound APIs. They specify how different types of traffic should be handled. These policies can be based on application priority, security requirements, or bandwidth limitations.

Network View and Path Computation

The SDN controller gathers information about the network state from connected devices via southbound APIs. It includes details like available bandwidth, link utilization, and device capabilities. Then, the controller calculates the optimal paths for data packets to transit the network based on the defined policies.

Flow Programming

The controller then issues instructions to the network devices through southbound APIs. These instructions, often called "flows," specify how to handle specific traffic flows, including the destination, priority, and any required security measures.

Programmable Forwarding

The network devices execute the received flow instructions. They inspect incoming data packets, match them to the programmed flows, and forward them along the designated paths without manual intervention.

Dynamic Monitoring and Adaptation

The SDN controller continuously monitors the network performance and collects device feedback. This real-time data allows the controller to identify any bottlenecks or changes in network conditions. In this way, the controller can dynamically adapt the flow programming to ensure optimal performance and policy adherence.

What are the Types of Software Defined Networking? 

Software-defined networking is available in versatile forms. Each of them has unique capabilities and benefits.

Open SDN- Standard Protocol-Based SDN

Open SDN utilizes open protocols to control virtual and physical devices to route data packets. Hence, this straightforward model relies on the open protocols like OpenFlow.

This type of SDN establishes vendor-neutral communication between the controller and network devices. Plus, it promotes interoperability and flexibility, empowering organizations to combine hardware from different vendors within the SDN ecosystem.


  • Cost-effective
  • Avoids vendor lock-in
  • Ideal for customized network configurations
  • Fosters innovation in open-source communities.


  • Requires deeper technical expertise for configuration and management
  • May necessitate additional tools for automation and orchestration.

API SDN – Vendor’s Controller-Based SDN 

It uses proprietary APIs specific to the vendor’s controller (Southbound APIs) instead of open protocols. In this way, API SDN allows the controller to manipulate remote devices using conventional methods (like SNMP or CLI or newer methods like REST API).

This type of software-defined networking offers a more controlled environment with guaranteed compatibility and simplified integration with existing vendor solutions.


  • Easier to deploy and manage
  • Provides strong performance and reliability within the vendor’s framework.


  • Limits choice and flexibility than open SDN
  • Restricts customization and integration with diverse network elements. 

Overlay Model SDN – Virtual Network

It creates a virtual network (VN) on top of the existing physical network infrastructure to provide tunnels containing channels to data centers. Then, this SDN allocates bandwidth in each channel and assigns devices to each channel. In this way, Overlay Model SDN creates a network over the physical network.


  • Offers rapid provisioning and isolation of virtual networks
  • Simplifies network migration and scalability
  • Ideal for managing network environments across on-premises, cloud, and hybrid deployments.


  • May introduce additional latency and complexity 
  • Requires specific overlay network software and expertise. 

Hybrid Model SDN – Combining SDN and Traditional Networking

The hybrid model combines SDN and traditional networking. It can support various functions on a network by assigning the optimal protocol for each type of traffic. Hence, it allows for gradually adopting SDN features within existing legacy network infrastructures. 


  • Minimizes disruption and investment in network overhaul
  • Facilitates phased integration of SDN benefits
  • Suitable for organizations with large installed bases of traditional equipment.


  • Complex network management and troubleshooting

What Are the Three Layers of an SDN?

Software-defined networking is built on three key layers. They work together to provide a flexible, programmable, and efficient networking solution.

Application Layer

This layer comprises network applications and services that utilize the SDN capabilities. It includes security tools, policy engines, and network management tools. Also, it has applications that interact with the controller to manage the network. 

All these applications relay information about the network or requests for specific resource availability or allocation. They interact with the Control Layer through interfaces known as north-bound APIs.

Examples: Firewalls, load balancers, intrusion detection systems, network analytics tools, and service orchestration platforms.

Control Layer

The Control Layer has the SDN controller as the brain of the network. Likewise, the SDN controller handles communication with the applications and determines the destination of data packets. It also allows hardware abstraction to the applications written on top of it.

This layer communicates with the Infrastructure Layer through southbound APIs. It receives input from the application layer and calculates optimal network paths based on real-time data. Then, it issues instructions to the underlying network devices.

Roles: Network view generation, path computation, flow programming, dynamic adaptation, policy enforcement.

Infrastructure Layer

This layer represents the underlying physical infrastructure (mostly the physical switches). These switches form the data plane and carry out the data packet movement. Hence, these networking devices receive instructions from the SDN Controller on how to route packets. 

The Infrastructure Layer provides a clear separation of the control and data planes. It enables greater flexibility and programmability in network management. This structure also enables centralized control over the network for efficient network operations and maintenance. 

Components: Physical cabling, server hardware, power systems, cooling systems.

Software Defined Networking vs. Traditional Networking

Software Defined Networking (SDN) and traditional networking differ in various aspects.

Advantages of Software-Defined Networking

Multiple benefits of SDN make it a compelling choice for modern networking solutions:

Advantages of Software-Defined Networking

Cost Reduction

SDN does not require a substantial investment. Some free-of-charge products are also out there. Thus, software-defined networking supports three-layer networking models. There is no need to purchase expensive networking devices. 

Overhead Reduction

In a physical environment, isolating customer workloads necessitates VLAN configuration on separate networking devices. And most of the networking is done at the SDN level. So, it is easier for service providers to isolate customer virtual machines from other customers using various methods. These methods are available in the SDN. 

Simplified Network Management

You can control virtual and physical networking using a central management tool in SDN. A virtual admin can process the necessary changes without collaboration with different teams. Likewise, this centralized approach provides a single point for network APIs. This way, SDN enables new use cases like network virtualization, automation, and verification.

Reduced Downtime

SDN supports snapshotting the configuration. It helps you quickly recover from any failures caused by upgrades. This networking architecture helps in virtualizing most of the physical networking devices. So, you can upgrade it to a one-piece device. 

Greater Control Over Network Traffic

SDN provides several isolation mechanisms, like configuring ACLs and firewalls at the virtual machine NIC level. Again, you can define the traffic rules using the SDN management console. It helps in providing full control over the network traffic.


As SDN is software-based, it is easy to use SDN API references for vendors to extend the capabilities of an SDN solution. They can develop applications to control the behavior of networking traffic. 


You can manage the traffic flow as need and usage fluctuates due to the dynamic load balancing of SDN. It reduces latency and increases the efficiency of the network. 


Network operators can perform several actions with the software-based control layer more flexibly. They can control the network, change configuration settings, provision resources, and increase network capacity. 

Enhanced SDN Security

Network admins can set policies from one central location as SDN enables it. In this way, they can determine access control and security measures networkwide. Besides, this centralized control enhances network security.

Simplified Multi-Cloud Management

SDN can simplify the management of hybrid and multi-cloud environments. It provides a centralized view and control of network resources across different cloud providers. This can improve agility and reduce complexity in cloud deployments.

Applications or Use Cases of SDN

You can use software-defined networking in different applications.

Use Cases


Data Center Optimization
  • Dynamic resource allocation
  • Automated provisioning and scaling
  • Traffic flow optimization
Cloud Networking
  • CSPs can offer dynamic, on-demand cloud services
  • Enterprises can manage hybrid and multi-cloud environments
  • Proper bandwidth allocation and network slicing 
Internet of Things (IoT) Networking
  • Management of IoT devices with their connectivity needs
  • Prioritize critical data flaws
  • Vibrant network changes
Software-defined wide-area Networks (SDWANs)
  • Simplification of branch office network management
  • Enabling centralized control and configuration
  • Dynamic traffic routing
Network Security
  • Granular policy enforcement or control over network traffic
  • Zero-Trust security models
  • Lower risk of unauthorized access and data breaches
Retail Innovation
  • Better in-store customer experiences
  • Hyper-fast WIFI for seamless mobile interactions
  • Bandwidth allocation optimization
  • Reliable connections for hospitals and healthcare facilities
  • Secure data transfer and smooth communication
  • Simplified network management 
Financial Services
  • Network latency optimization for various applications
  • Firewall rules adjustments based on market conditions
  • Better network resilience
  • Bandwidth allocation for online learning platforms
  • Limiting access to unauthorized websites
  • Network resource allocation and adjustments

Implementing Software Defined Networking

You can use software-defined networking in different applications. 
Implementing Software Defined Networking

Software Defined Networking Security: Benefits and Challenges

SDN indeed offers multiple security benefits. Yet when you implement it, you may face some challenges that you must manage to get the best of it.

Security Advantages of SDN

Granular/Centralized Control and Visibility
Define security rules at the flow level, segment the network, and restrict access to specific resources to create micro-perimeters that minimize attack surfaces.

Real-time Monitoring

The centralized controller enables real-time monitoring and detection of anomalies and suspicious activity.
Dynamic Threat Mitigation
Adapt your security posture dynamically to evolving threats by adjusting firewall rules and rerouting traffic away from compromised segments. 
Enhanced Security Services Integration
Integrate SDN with advanced security tools like intrusion detection and prevention systems (IDS/IPS), firewalls, and encryption solutions for strong defense against cyberattacks. 

Security Challenges of SDN

Centralized Control Vulnerabilities

The entire network can be at risk if the control plane is compromised. 

API Security

APIs help SDN controllers communicate with network devices and apps. However, network attackers can target these APIs. 


Integrating SDN with existing security infrastructure can be complex. 

Nybsys Software Defined Networking (SDN)

We, Nybsys, offer the finest software-defined networking (SDN) implementation. We focus on reforming network management through automation. Also, our SDN can easily and seamlessly integrate with your existing infrastructure and tools. 

Nybsys SDN provides robust security with features like centralized traffic control, micro-segmentation, and threat detection. Besides, the user-friendly interface helps to manage the network easily.

Simply consider your specific needs like automation, security, cloud integration, etc. Then, let us know – our entire team is ready to welcome you! So, why wait?

Frequently Asked Questions

Traditional networking involves a rigid, hierarchical architecture. The control and data planes are bound together on the same device in this networking. This structure can be difficult to modify or adapt to changing business needs. Alternatively, SDN separates the control plane from the data plane. This separation allows for greater flexibility and control over network traffic..
SDN improves network performance by providing centralized control over network traffic. This centralized control allows for more efficient use of network resources, better load balancing, and quicker failure recovery.
Network Functions Virtualization (NFV) complements SDN by virtualizing network functions. It allows deploying virtual network functions (VNFs) instead of traditional physical network devices.

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