What is software-defined networking (SDN)?

2023.12.21

SDN is the abbreviation of Software Defined Network, which is a network architecture that separates the control plane and data plane. It involves decoupling network intelligence and policy from the underlying network infrastructure, providing a centralized management and control framework.

How does software-defined networking (SDN) work?

SDN operates by employing a centralized controller that manages and configures network devices, such as switches and routers, through open protocols such as OpenFlow. The controller acts as the brains of the network, allowing administrators to centrally define network behavior and policies and then enforce them across the entire network infrastructure. SDN networks can be divided into three layers, each layer consisting of different components.

Application layer: The application layer contains the network applications or functions used by the organization. There may be multiple applications related to network monitoring, network troubleshooting, network policy, and security.

Control layer: The control layer is the middle layer that connects the infrastructure layer and the application layer. It refers to the centralized SDN controller software that serves as the land of the control plane, with intelligent logic connected to the application plane.

Infrastructure layer: The infrastructure layer consists of various network devices, such as network switches, servers, or gateways, which form the underlying network and forward network traffic to its destination.

To communicate between the three layers of an SDN network, northbound and southbound application programming interfaces (APIs) are used. The northbound API implements communication between the application layer and the controller, and the southbound API implements communication between the controller and network devices.

What are the different models of SDN?

According to the connection method between the controller layer and SDN devices, SDN networks can be divided into four different types, and we can classify them as follows:

OpenSDN

OpenSDN has a centralized control plane and uses OpenFlow as the southbound API for traffic from physical or virtual switches to SDN controllers.

SDN API

APISDN is different from open SDN. Rather than relying on open protocols, application programming interfaces control how data moves across the network on each device.

Overlay SDN

Overlay SDN does not solve the underlying physical network, but builds a virtual network on top of current hardware. It operates on an overlay network and provides tunnels with channels to the data center to solve data center connectivity issues.

Hybrid SDN

Hybrid SDN, also known as automation-based SDN, combines SDN features with traditional network equipment. It uses agents, automation tools like Python, and components that support different types of operating systems.

What are the advantages of SDN?

Different SDN models have their own advantages. Here, we will only discuss the general benefits of SDN to networks.

Centralized management

Centralization is one of the main advantages of SDN. SDN networks enable centralized management of the network using central management tools, from which data center managers can benefit. It breaks down barriers created by legacy systems and provides greater flexibility for virtual and physical network configurations, all from a central location.

Safety

Although the virtualization trend makes it more difficult to protect networks from external threats, SDN brings significant advantages. SDN Controller provides network engineers with a centralized location to control the entire security of the network. Through the SDN controller, ensure that security policies and information are implemented within the network. And SDN comes with a single management system, which helps enhance security.

save costs

SDN networks provide users with low operating costs and low capital expenditure costs. On the one hand, the traditional way of ensuring network availability is through redundancy of additional equipment, which of course increases costs. Compared with traditional methods, software-defined networks are more efficient and do not require the purchase of more network switches. On the other hand, SDN works well with virtualization, which also helps reduce the cost of adding hardware.

Scalability

SDN provides users with more scalability since OpenFlow agents and SDN controllers allow access to various network components through their centralized management. Compared to traditional network setups, engineers have more options to make immediate changes to network infrastructure without having to manually purchase and configure resources.

In summary, SDN plays a vital role in modern data centers where agility and efficiency are crucial. By virtualizing network resources, SDN enables administrators to automate network management tasks and streamline operations, thereby increasing efficiency, reducing costs, and accelerating time to market for new services.

SDN is changing the way data centers operate, providing tremendous flexibility, scalability and control over network resources. By adopting SDN, organizations can unlock the full potential of their data centers and stay ahead of the curve in an increasingly digital and connected world.