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What Is Software-defined Networking?

Software-defined Networking

What Is Software-defined Networking?

Software-defined networking (SDN) is networking technology that uses APIs and software-based controllers to manage, automate, provision, and program network resources for improved network control and management.

What Is Software-defined Networking?

SDN abstracts the network control plane (which determines where to route network traffic) from the data plane (which forwards the data through network hardware such as routers) and centralizes the management of the network using a software-based controller. 

As a result, network administrators can program and control the entire network using a central server instead of on a device-by-device basis, making the network more flexible and easier to manage.

How Software-defined Networking Works?

An SDN architecture comprises three key elements: the application layer, the control layer, and the infrastructure layer. Let’s look at each layer in more detail.

The Application Layer

The application layer of an SDN architecture contains network-related applications such as firewalls, load balancers, cybersecurity, and other business applications. These applications communicate resource requests and specific network instructions to the SDN controller.

The Control Layer

The control layer contains the centralized SDN controller, which uses northbound APIs to relay information between the controller and application layer, and southbound APIs which enable communication between the controller and each physical network device in the infrastructure layer.

The Infrastructure Layer

This layer comprises physical or virtual infrastructure such as switches, access points, and routers. The network infrastructure in this layer receives instructions from the SDN controller on how to route data packets.

Traditional vs. Software-defined Networking: Differences

Traditional networks use dedicated hardware devices like routers and switches to control network traffic. The control plane and the data plane are tightly coupled and mounted on the same plane. As a result, network upgrades and changes are time-consuming because administrators must apply changes manually on each device.

SDN uses software and APIs to control network traffic and handles network control completely through the abstracted control plane. This allows network administrators to configure settings, provision resources, and manage the overall network from a single central interface, without adding additional hardware.

Intent-based vs. Software-defined Networking: Differences

An intent-based network (IBN) is a network administration approach that uses artificial intelligence (AI), machine learning (ML), and orchestration to automate the creation, management, and enforcement of network policies. 

SDN, on the other hand, moves from the traditional hardware-based network to a software-enabled network that allows users to program how network devices work. IBN aims to create an automated, network orchestration solution based on business objectives, using AI and ML to determine which devices and routes match the business intention. In this way, IBN incorporates and builds upon SDN, adding another level of abstraction and automation.

Traditional Networking vs. SDN vs. IBN: Comparison


Software-defined Networking

Intent-based Networking

Network Infrastructure

Physical hardware comprising switches and routers

Virtualized components

Virtualized; uses SDN principles and architecture as a foundation

Ease of Management

Manual configuration must be done for each device

Centralized control plane for management, configuration, and provisioning of network resources

Aims to create a fully autonomous network  based on business intent using AI, ML, and network orchestration


Control and data plane mounted on the same hardware device

Control plane abstracted from data plane using software

Abstracts the management control plane at a higher level, making it more business-centric

Programmability & Automation

Static and inflexible with no programmability

Centrally programmable; can easily handle changing network requirements and maintenance tasks

Uses AI and ML to orchestrate network commands and tasks based on business objectives


Each device is configured and managed separately; lacks visibility

Centralized management and configuration from a single pane of glass

Uses SDN controllers for centralized management and configuration


Benefits of Software-defined Networking

SDN offers several advantages to organizations, including all of the following:

Centralized Management

SDN’s centralized controller allows engineers and administrators to manage the network and policies without having to configure individual devices. Administrators can allocate network resources and configure network-wide services such as access control and security policies from a central location.

Greater Scalability

SDN gives administrators more control over network resources and traffic flow allowing them to adjust infrastructure and configurations to meet changing business needs. Administrators have the flexibility to add or remove virtual devices, adjust configurations, and control traffic across the SDN architecture quickly and seamlessly without having to change the physical infrastructure.

Increased Visibility

SDN gives organizations a global view of their network. With greater visibility into the network and the ability to control and monitor network traffic from a central location, administrators gain a holistic view of the network to monitor the overall performance and identify potential security threats.

Improved Efficiency

SDN reduces network complexity, increasing the speed and efficiency of network management. Administrators can quickly and easily automate network functions and provide resources to support faster innovation, decreasing time to market. Real-time visibility into network performance also allows you to optimize network performance for more efficiency.  

Cost Savings

Because SDN uses virtualized resources, it eliminates the capital expense (CAPEX) associated with purchasing and upgrading costly hardware. Using virtual network components also reduces operating expenses (OPEX) because there are no physical devices to maintain, configure, and upgrade, leading to a reduced total cost of ownership (TCO).

Disadvantages of Software-defined Networking

SDN provides several important benefits, but there are also a few disadvantages that should be considered.

Controller Vulnerability

SDN’s use of a centralized virtual controller creates a potential single point of failure in the network. If a breach occurs at the controller level, it can potentially propagate to other network infrastructure. Because of this, it’s crucial to monitor access to the controller and implement controller redundancy and automatic failover.

Increased Latency

As organizations add more resources to the SDN architecture, the speed of interaction between the controller and the devices may decrease. This complexity can lead to controller overload, which increases network latency and reduces the overall reliability of the network.

Device Security

Even though SDN increases visibility and by extension, security of the entire network, it lacks the security mechanisms that typically come with physical routers, switches, and firewalls. This increases the vulnerability of the network to external threats.

SDN Use Cases

Here are a few common scenarios where SDN can be used to solve networking challenges.

New Corporate WAN

When implementing a new wide-area network (WAN), consider using SDN-compliant network equipment. With SDN, you can better handle the different types of traffic, QoS, or VPN routing requirements for multiple end-user applications.

Google has used SDN in its WAN since 2012 to interconnect its data centers, collaborating with the Open Networking Foundation in 2018 to develop four new interfaces to replace OpenFlow, the original protocol for SDN.

Upgrading an Existing Network

As the infrastructure of a physical network becomes obsolete, consider adding SDN-compliant products to support greater operational efficiency, business expansion, programmability, and service efficiency. 

For example, when upgrading network hardware, an SDN solution can simplify network management, tighten security, and facilitate internet of things (IOT) across several buildings and approximately 2,000 users.

Scalable Data Centers

SDN can also help enterprises scale to manage data storage and consumption more efficiently. This can include deploying a new data center in a matter of hours and provisioning network resources in minutes, instead of weeks.

Software-defined Networking FAQ

Can I install SDN alongside my existing network?

Yes. SDN can be used with a traditional network via an orchestration platform that can bridge the legacy and SDN infrastructure. This can be a gateway device that allows the SDN domain to flow through to the legacy network or by using hybrid switching, which can handle both OpenFlow and traditional networking, splitting the ports between the two domains.

Are SDN and SD-WAN the same?

SDN focuses primarily on abstracting network infrastructure in a local area network (LAN) such as a data center within the enterprise perimeter or a service provider’s core network. Alternatively, SD-WAN provides software-defined application routing across a wide geographical area to connect data centers, branch offices, and remote users on a national or global level.

How does SDN support today’s networking needs?

SDN supports several features required by modern applications in today's networks. These include the ability to move data between distributed locations, shift workloads between private and public cloud infrastructure, quickly add or remove network resources, and deliver the speed and flexibility to support emerging technologies such as edge computing and IoT.

Gain Agility, Portability, and Visibility with Software-defined Storage

Software-defined networking is part of a growing industry trend that includes software-defined storage (SDS) and other software-defined infrastructure that help businesses separate how a resource is managed (control plane) from how it is accessed (data plane) to achieve greater agility, portability, and visibility.

Pure Storage® Purity is a high-performance software-defined storage solution that enables you to decouple storage hardware from software for more flexible and agile storage. With Purity, you can leverage the benefits of software-defined storage to:

  • Monitor and optimize storage from a single interface.

  • Seamlessly move workloads between cloud and on premises to meet changing business requirements.

  • Create a unified storage solution by consolidating workloads and aggregating data.

  • Leverage the predictable, high speeds of Pure’s all-flash storage arrays for enterprise apps and workloads.
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