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Difficulty: HardComparing Traditional Networks with Controller-Based Networking

A network administrator is evaluating the operational architecture of a software-defined networking (SDN) deployment compared to an existing traditional campus infrastructure. The management application needs to push business intent and policy changes dynamically to a centralized SDN controller, which subsequently programs the physical network devices across the fabric. Which statement accurately describes the interface roles and communication protocols used in this controller-based architecture?

  1. Northbound APIs use RESTful HTTP calls to communicate intent between management applications and the controller, while Southbound APIs use protocols such as NETCONF or RESTCONF to program the network devices.Answer
  2. B
    Southbound APIs rely exclusively on HTTP GET requests initiated by network switches to pull configuration updates directly from business management applications.
  3. C
    The control plane remains distributed across each edge device, while Northbound APIs execute SSH scripts directly on switch CLI interfaces to synchronize forwarding state.
  4. D
    Northbound APIs utilize RADIUS payload encapsulation to pass low-level MAC address tables directly to data plane hardware switches.

Answer

Northbound APIs use RESTful HTTP calls to communicate intent between management applications and the controller, while Southbound APIs use protocols such as NETCONF or RESTCONF to program the network devices.
In a software-defined controller-based network, the control plane is centralized within the SDN controller. Management applications communicate with the controller via Northbound APIs (typically RESTful APIs using HTTP/HTTPS). The controller then translates application requests into network device configurations and communicates down to physical switches and routers via Southbound APIs (using protocols such as NETCONF, RESTCONF, or OpenFlow) to update data plane forwarding behavior.

Step-by-Step Solution

1
Analyze the SDN control plane abstraction architecture
Identify that controller-based networking splits architectural interaction into Northbound (above the controller) and Southbound (below the controller) interfaces.
Traditional networks run control plane protocols locally on each device, whereas SDN centralizes control logic on a controller positioned between management apps and network hardware.
2
Evaluate Northbound API functions and protocols
Determine that applications program network intent into the controller via RESTful APIs using standard HTTP verbs (GET, POST, PUT, DELETE).
Northbound APIs abstract underlying topology details and expose programmatic interfaces to higher-level orchestrators.
3
Evaluate Southbound API functions and protocols
Determine that the controller uses Southbound mechanisms (NETCONF, RESTCONF, gNMI, OpenFlow) to communicate policies to physical switches and routers.
Southbound protocols relay control instructions down to the data plane hardware to update forwarding tables.

Key Concept

Comparing Traditional Networks with Controller-Based Networking
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Topics

Comparing Traditional Networks with Controller-Based Networking

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