What is Software Defined Networking (SDN)?

Software Defined Networking (SDN) has emerged as a revolutionary approach in the field of networking, promising unprecedented flexibility, efficiency, and scalability.

In a rapidly changing technological landscape, the traditional way of managing networks has become cumbersome and limiting. Organizations are now turning to SDN as a solution to their networking challenges. But what exactly is SDN and why is it causing such a stir in the industry?

In this blog post, we will delve into the essence of SDN, exploring its fundamental principles, benefits, and potential drawbacks. By the end, you will have a clear understanding of what SDN is and how it can transform the way networks are designed, managed, and operated.

Meaning of Software-Defined Networking

Software-defined networking is a networking architecture wherein a lot of networking functions are implemented in software. It makes all networking functions programmable, and hence, many networking functions are being added to this architecture. Software-defined networks are usually faster than traditional data centre architecture.

When all networking functions are implemented in software, it makes it possible to apply many policies to make the network perform per the needs of the company. These policies can be changed quickly. This is beneficial to the company as it does not need to invest in new hardware and networking architecture to achieve its goals.

How Does Software Defined Networking Work?

Traditional Networking usually relies on fixed-function network devices, e.g. Switch, Router, MPLS switch, FC Switch, FCoE switch, and Ethernet Switches. All these have a specific function and coordinate with each other to make your network work. It is faster because most parts are implemented as hardware constructs fast. The only “problem” is flexibility, which is more hyped than true because of non-technical reasons.

Traditionally all switching hardware and software have been proprietary, with not much of APIs exposed for provisioning. Even though they are told it usually works well with proprietary provisioning software, which can’t be changed swiftly according to the user(at least not if they have a small wallet).

Software Defined Networking, on the other hand, as I look at it, is adding a lot of programmability to the network. This could not be done on fixed-function switches as hardware is not subject to rapid transitions(Barefoot Networks and Cavium are changing this). Hence, the control plane, or the decision-making part, was offloaded to software, making it slower but more flexible as it can be changed and can talk to applications in a much better way than a traditional switch. This helps people with a small wallet as they can take a white box switch, install an OpenFlow(or any southbound SDN) based OS, build their own controller, and use it to programme the switch.

This all sounds very good, but it does not work well and has not been able to beat traditional networking solely because traditional networking is tried and tested and is lightning fast compared to SDN. On the other hand, software-defined networking has the bottleneck of software. In computing, the industry was Network along with Von-Neuman bottleneck are the two most famous bottlenecks; SDN just makes the bottleneck more with only added the advantage of programmability.

Let’s take a look at some of the features that define the SDN, along with the benefits they promise to deliver.

SDN vs Legacy

Networks are built around equipment such as routers, switches, and firewalls. The control and data planes are baked into these hardware devices. The control plane determines where the traffic is sent. The data plane forwards that traffic based on how the control plane is configured. Making changes to the network configuration requires new hardware and more configuration. Legacy networks also do not respond efficiently to changing network conditions. Today that is important as virtualisation and mobility work best on dynamic networks.

SDNs take a page out of the server virtualisation playbook and insert an abstraction layer. This layer separates the control plane from the data plane. SDN effectively decouples the hardware from the software layer. This separation makes network virtualisation a reality because you are no longer executing control roles on the hardware devices. Legacy networks take time and effort to modify. SDNs promise administrators the ability to shape the network any way they want. The SDN also gives administrators the ability to set the rules and controls through a software interface.
Network administrators will embrace SDN because it allows for granular control of network traffic. It also promises to decrease reliance on hardware with proprietary firmware to perform these functions.

How is SDN being used?

The concept of SDN is widely used in data centres and other large-scale networks. The big data centres that are used by data centres have been using software-defined networking. The data centres are now becoming more intelligent and more scalable. The network functions of the data centres are now being managed from a centralised location.

Many service providers are also using software-defined networks. These include mobile operators, who can change their network and the location of the base station on-the-fly as required. This allows the network to be scaled up without needing an upgrade of the network architecture.

Why is software-defined networking getting more popular?

One of the key reasons why SDN is getting more popular is that the number of network devices that are being used in companies and other organisations is increasing. Most network devices are now being connected to the network via the Ethernet interface.

Another reason SDN is getting more popular is that many features are being added to this architecture. Some of these features include:

  1. The virtual networks that are being created are being connected to the existing network via a virtual switch. This makes it possible to connect all these networks to the existing network. It also helps to reduce the cost of setting up a new network.
  2. The SDN can be connected to the cloud, which provides resources to the users. This allows the users to connect to the network as and when they need to. They can also connect to the cloud from any place as and when they wish to. This is beneficial to the users because they can access the network from any place as and when they wish to.
  3. The virtual private networks can be created in the SDN. This can be used to create virtual private networks in a public network. It helps to secure private networks by using the existing network.

The Benefits of Software Defined Networking

There are many benefits of using software-defined networking. These benefits can be enumerated in the following points:


This is the key feature of SDN. Since all networking functions are programmable and can be changed as required, it provides a lot of flexibility to the network administrator. It is also scalable as the network can be expanded, and new networking functions can be added as required.


Network engineers used to spend a lot of time troubleshooting the network. With software-defined networking, the network can be monitored in real-time. It is also possible to change the network performance automatically without human intervention. This makes it possible to achieve high levels of automation.


SDN makes it possible to expand the network without having to invest in more powerful hardware. As a direct consequence of this, both the number of network links and the associated costs have been reduced.

Improved Performance

Utilizing software-defined networking results in an improvement in the overall performance of the network. This is because every network function can be programmed, allowing for changes to be made instantly. Because of this, it is now possible to make adjustments to the network in real-time as and when they become necessary.

Increased Security

Because of SDN, the network administrator can also implement security measures and conduct intrusion detection. A centralised management system allows the network’s settings and administration to be managed with ease.

Disadvantages of Software-Defined Networks

The most significant advantage of SDN today is that it is still mostly unproven. A lot of the benefits cited by companies with investments in the underlying technology are theoretical. That does not mean they will not work in practice, but it is too early to know for certain. Networking tools have been evolving for more than 50 years. Whenever a new technology arrives and promises to overhaul the incumbent, there are bound to be a few naysayers. I liken SDN to where the cloud was about a decade ago.

Another issue SDN will have to work through is its reliance on software. Hardware is expensive and takes time to configure. However, once optimized, it works for a long time. The software is buggy and requires developers to maintain it. The reliability of your network relies on the stability of the software managing it. Moving the intelligence from the hardware to the software layer sounds great in theory. Moreover, when it works, it will be a dream for administrators. However, when it goes down, that dream will turn into a nightmare.


Software-defined networking (SDN) is a key component of IT infrastructures in cloud-native enterprises. Using the principles of virtualization to virtualize your network, SDN allows you to change network behaviour, such as adding, removing, and/or controlling network elements, according to defined policies.

This means that you are no longer tied to specific hardware for your networking. Software-defined networks enable automation and customization. And as SDN technology has evolved, so has the complexity of infrastructure and associated tools. In addition to SDN hardware, many SDN solutions now include open source tools for network automation and configuration.

With so many companies investing in SDN and Network Function Virtualization (NFV) and so much revenue to be tapped, I believe that SDN will most definitely prevail in the industry because none of the recent past technologies (for example, GMPLS) has captured the attention of the industry as SDN has.

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Raj Maurya

Raj Maurya is the founder of Digital Gyan. He is a technical content writer on Fiverr and When not working, he plays Valorant.

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