SDN API Technology for Controller and Device Communication
Short answer
C Southbound APIs are the technology used to communicate between the SDN controller and network devices such as routers and switches.
Question
Key Takeaways
The core concept tested is the directional flow of SDN APIs; the common trap is confusing northbound APIs (controller to applications) with southbound APIs (controller to infrastructure).
This question examines the role of southbound APIs in Software-Defined Networking (SDN) architectures, which facilitate communication between the central controller and underlying network devices like routers and switches.
Common mistake: Candidates often select 'northbound APIs' because they are more frequently discussed in application integration contexts, failing to distinguish that southbound APIs specifically target the data plane devices.
Expert Analysis
Why the Answer Is Correct
Southbound APIs serve as the interface between the SDN controller and the network infrastructure elements, such as routers, switches, and firewalls. They allow the controller to program the forwarding behavior of these devices, effectively separating the control plane from the data plane.
Why the Other Options Are Wrong
Northbound APIs provide an interface for applications and business logic to communicate with the SDN controller, not the network devices themselves. REST APIs are a specific architectural style often used to implement these interfaces but do not define the directional relationship in SDN topology. Unprotected APIs are insecure and not a standard functional category for legitimate SDN operations.
Community Comment Notes
Community consensus strongly supports option C. As XBfoundX noted, Southbound APIs relay information directly between the controller and individual network devices like switches and routers, confirming the definition found in Cisco SDN documentation.
Official Reference
https://www.cisco.com/c/en/us/solutions/software-defined-networking/overview.html#~what-is-sdn
This link opens the official vendor documentation in a new tab.
Exam Strategy
When analyzing SDN components, always identify the direction of traffic: 'North' goes up to apps/business logic, while 'South' goes down to the hardware infrastructure. Memorize this directional metaphor to quickly eliminate wrong options.
Frequently Asked Questions
What is the difference between northbound and southbound APIs in SDN?
Are REST APIs considered southbound APIs?
Discussion 2 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 2
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XBfoundX 👍 1 Answered CSouthbound APIs that relay information between the controller and the individual network devices (such as switches, access points, routers, and firewalls) https://www.cisco.com/c/en/us/solutions/software-defined-networking/overview.html#~what-is-sdn
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klu16 👍 1 Answered CIt's C.
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