Question

What is SDN? Explain SDN architecture along with Operations of control and data planes.

Answer 1

Software-Defined Networking (SDN):

Software-Defined Networking (SDN) is an innovative approach to network management that allows network administrators to control and manage network resources dynamically using software applications. SDN separates the control plane, which makes decisions about where to send traffic, from the data plane, which actually forwards the traffic to its destination. This separation provides greater programmability, flexibility, and control over the network infrastructure.

SDN Architecture:

The SDN architecture typically consists of three key components:

1. Application Layer:

   • SDN applications are responsible for defining the network policies and services.
   • These applications communicate with the SDN controller to convey their requirements.

2. SDN Controller ( Control Layer ):

   • The SDN controller is the brain of the SDN architecture, responsible for making decisions about where to send traffic based on the policies defined by the applications.
   • It communicates with both the application layer and the network devices in the infrastructure.

3. Infrastructure Layer:

   • The infrastructure layer includes the physical and virtual network devices, such as switches and routers.
   • These devices forward the traffic based on the decisions made by the SDN controller.

Operations of Control and Data Planes:

1. Control Plane Operations:

   • Policy Decision: The control plane, managed by the SDN controller, receives network policies and requirements from SDN applications.
   • Network Topology Discovery: The controller gathers information about the network topology, including the status of links and devices.
   • Path Computation: Based on policies and network topology, the controller computes the optimal paths for data transmission.

2. Data Plane Operations:

   • Packet Forwarding: In the data plane, network devices (switches, routers) forward packets according to the paths determined by the SDN controller.
   • Flow Table Updates: The SDN controller updates flow tables in network devices to reflect changes in network conditions or policies.
   • Packet Processing: As packets arrive at network devices, they are processed based on the rules set by the controller, ensuring adherence to network policies.