SDN (Software defined networking)

Software-Defined Networking (SDN) is a networking paradigm that separates the control plane from the data plane in network devices, enabling centralized control and programmability of the entire network infrastructure. In traditional networking, the control plane and data plane are tightly integrated within network devices, such as routers and switches. SDN decouples these two planes, allowing for greater flexibility, scalability, and automation in network management.

To understand SDN, let's break down the components and concepts involved:

1. Control Plane: The control plane is responsible for making decisions about how network traffic should be forwarded. It handles tasks like routing protocols, network topology discovery, and traffic engineering. In SDN, the control plane is centralized in a software-based controller that has a global view of the network.
2. Data Plane: The data plane is responsible for forwarding network traffic based on the decisions made by the control plane. It consists of the network devices, such as switches and routers, that physically move packets across the network.
3. SDN Controller: The SDN controller is the brain of the SDN architecture. It is a software application that runs on a server or a cluster of servers and acts as the central point of control for the entire network. The controller communicates with network devices using a standardized protocol, such as OpenFlow, to configure their behavior.
4. OpenFlow: OpenFlow is a widely adopted protocol that allows the SDN controller to communicate with network devices. It defines a standard way of programming and controlling the forwarding behavior of switches and routers. The controller can instruct network devices on how to handle packets, including forwarding, filtering, and modifying headers.
5. Southbound Interface: The southbound interface refers to the communication link between the SDN controller and the network devices in the data plane. OpenFlow is an example of a southbound interface protocol used in SDN.
6. Northbound Interface: The northbound interface provides an interface for applications or network management systems to interact with the SDN controller. It allows external entities to request network services or provide instructions to the controller. The northbound interface can use APIs (Application Programming Interfaces) or other protocols to enable this communication.
7. Network Operating System (NOS): The NOS is the software that runs on network devices and provides the necessary functionality to participate in an SDN architecture. It typically includes an OpenFlow agent or module to communicate with the SDN controller.
8. Network Virtualization: SDN enables network virtualization, which allows the creation of virtual network overlays on top of the physical infrastructure. Virtual networks can be dynamically created, modified, or removed based on the requirements of applications or tenants. This flexibility is particularly useful in cloud computing environments.
9. Centralized Network Management: SDN provides a centralized management and control plane, allowing network administrators to have a global view of the network and configure network policies from a central location. This simplifies network management tasks and enables automation through programmability.

Benefits of SDN:

• Simplified network management: SDN centralizes control and provides a single point of management, making it easier to configure and manage network devices.
• Increased agility: SDN enables rapid provisioning of network services and allows for dynamic reconfiguration of network policies based on changing requirements.
• Enhanced scalability: SDN provides a scalable architecture that can adapt to growing network demands without requiring significant hardware upgrades.
• Cost savings: By abstracting network functions from the underlying hardware, SDN enables the use of commodity switches and routers, reducing costs.
• Improved security: SDN allows for fine-grained control and monitoring of network traffic, making it easier to implement security policies and detect anomalies.

Overall, SDN revolutionizes the way networks are designed, managed, and operated by separating the control plane from the data plane, providing centralized control, and enabling programmability and automation.