What is Software Defined Networking (SDN)?

Is Network Design Programmable?

In traditional networks, each networking device (like switches and routers) has its own brain, called the control plane, which decides how to handle data. It's like players on a team making individual decisions during a game without a central strategy. This makes it impossible to dynamically make decisions on the network as the network condition changes, making it difficult for network administrations to react to the elevated traffic volumes immediately.

SDN changes this by introducing a central brain, known as the controller, which acts as the control plane for the entire network. The controller communicates with each device's control plane, guiding the decisions of the devices. This separation of the control plane from individual devices makes communication and decision-making more centralized and efficient.

Now, imagine the data plane as the players executing the decisions made by the control plane. In traditional networks, each player (device) decides on its own moves based on its control plane. SDN, however, allows the central controller to guide all players simultaneously, ensuring a coordinated and strategic approach.

One common problem in traditional networks is that if you want to change the game plan, you have to talk to each player's control plane individually. It's time-consuming and can lead to mistakes. SDN solves this by letting you talk to the coach (controller), who then instructs the control planes of all devices at once, affecting the entire team's strategy. This way the routing policies and prioritization of the data packets are dynamically managed by the central control plane and its all executed in real time.

This approach, with a centralized control plane, coordinated data plane actions, and using protocols like OpenFlow for communication, makes it easier to adapt to changes, troubleshoot issues, and improves overall efficiency in network management. Additionally, concepts like network virtualization enable the creation of virtual networks, and understanding the broader SDN ecosystem and industry standards ensures compatibility and effective implementation.

Exploring further, Northbound and Southbound APIs facilitate communication between the SDN controller and applications (northbound) and between the controller and network devices (southbound), resembling how the coach communicates with both the team and the game field. Practical applications, such as network slicing and cloud connectivity, showcase SDN's real-world impact, similar to seeing how the game plan works in various game scenarios. Moreover, recognizing potential challenges in implementing SDN, including scalability and security considerations, adds practical awareness, similar to acknowledging potential hurdles a team might face during the game.

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