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Difficulty: MediumComparing Traditional Networks with Controller-Based Networking

During a network topology change in an enterprise environment, a network team evaluates how routing updates are processed. In a traditional distributed network, each router independently recalculates its routing table using its local control plane. Which statement correctly describes how control plane processing is handled in a controller-based network during the same topology change?

  1. The centralized controller calculates the updated topology paths and uses Southbound protocols to update the forwarding tables on the network devices.Answer
  2. B
    Network devices execute HTTP GET requests northbound to push their newly calculated local link-state topology tables to the central controller.
  3. C
    Each network switch relies on an agent-based architecture where local control plane engines compute topology tables independently before syncing with the controller.
  4. D
    The controller broadcasts raw JSON array strings to the data plane, requiring individual switch CPUs to parse JSON key-value pairs to determine forwarding decisions.

Answer

The centralized controller calculates the updated topology paths and uses Southbound protocols to update the forwarding tables on the network devices.
In controller-based networking, control plane intelligence is centralized. When a topology event occurs, the controller processes the change globally, calculates updated paths, and programs the new forwarding entries directly into device data planes using Southbound protocols.

Step-by-Step Solution

1
Analyze the control plane architecture in traditional versus controller-based networks.
Traditional networks rely on a distributed control plane where each node independently computes routing paths. Controller-based networks centralize control plane intelligence onto an SDN controller.
Identifying the control plane location is the fundamental step in contrasting SDN with traditional networking.
2
Determine how updated forwarding decisions reach the physical devices in an SDN environment.
The SDN controller computes the global path changes and uses Southbound APIs (e.g., OpenFlow, NETCONF, RESTCONF) to program the data plane of managed devices.
Southbound APIs serve as the interface between the centralized controller and the underlying network hardware.

Key Concept

Centralized Control Plane and Southbound API Operations in Controller-Based Networking
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Topics

Comparing Traditional Networks with Controller-Based Networking

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