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Difficulty: MediumComparing Traditional Networks with Controller-Based Networking

A network engineer is evaluating the architectural shift from legacy autonomous switches to a centralized Software-Defined Networking (SDN) model for a campus deployment. Which statement accurately describes how control plane operations and traffic handling differ in a controller-based network compared to a traditional network architecture?

  1. Control plane intelligence is centralized within the software controller to program policies and forwarding instructions, while individual network devices perform high-speed data plane packet forwarding.Answer
  2. B
    Control plane decisions remain distributed across individual switch CPUs, while all data plane packet forwarding is centralized and handled directly by the controller.
  3. C
    Management applications use Southbound REST APIs to dynamically recalculate the physical network topology at the data plane layer of each autonomous router.
  4. D
    Individual network devices use agent-based configuration management to process data plane path selection, eliminating the need for Southbound interfaces.

Answer

Control plane intelligence is centralized within the software controller to program policies and forwarding instructions, while individual network devices perform high-speed data plane packet forwarding.
In controller-based networking (SDN), control plane decision-making is decoupled from local network devices and centralized within the controller. The controller maintains a global view of the network and programs the forwarding tables on physical network devices via Southbound APIs. The physical switches and routers continue to perform hardware-based data plane packet forwarding.

Step-by-Step Solution

1
Analyze traditional network architecture roles
In traditional networking, every router and switch operates distributed control, management, and data planes locally on the device.
Each node runs individual routing protocols (e.g., OSPF) to independently populate its own forwarding table.
2
Compare controller-based (SDN) plane separation
Controller-based networks decouple the control plane from distributed devices and centralize it onto an SDN controller (e.g., Cisco DNA Center / Catalyst Center).
Centralization allows global topology awareness and policy enforcement, while network elements (switches/routers) retain only the data plane for forwarding packets based on controller instructions.
3
Select the option describing this plane decoupling correctly
The statement highlighting centralized control plane policy generation paired with distributed data plane hardware forwarding accurately reflects SDN design.
It correctly identifies the operational roles of the controller and network devices.

Key Concept

Separation and centralization of control plane functions in controller-based SDN architectures versus distributed control planes in traditional networks.
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Comparing Traditional Networks with Controller-Based Networking

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