In SDN architecture, what is the primary role of the control plane?
2023
In SDN architecture, what is the primary role of the control plane?
Answer: B. To manage flow rules and make decisions about where traffic should go — Concept — The work a network does splits into planes. The control plane is the decision layer: it builds a view of the network, computes paths and writes the…
- A.
To forward packets based on routing tables
- B.
To manage flow rules and make decisions about where traffic should go
- C.
To physically connect different network devices
- D.
To encrypt data before transmission
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Correct answer: B
Concept — The work a network does splits into planes. The control plane is the decision layer: it builds a view of the network, computes paths and writes the forwarding entries that devices will use. The data (forwarding) plane is the execution layer: it moves each arriving packet out of a port by looking those entries up. Software-Defined Networking (SDN) pushes this split further by lifting the control plane out of the individual devices into a logically centralised controller.
Application — In an SDN network the controller keeps a global view of the topology, decides which path traffic should take, and installs the resulting flow rules into every switch’s flow table over a southbound interface such as OpenFlow. The primary role of the control plane is therefore to manage flow rules and decide where traffic should go, while each switch is left with the fast lookup-and-forward job.
Cross-check — Each activity below belongs to a different part of the system:
Activity | Where it belongs |
|---|---|
Forwarding a packet against installed table entries | Data (forwarding) plane inside the switch |
Managing flow rules and choosing traffic paths | Control plane, centralised in the SDN controller |
Physically connecting devices | Cabling, connectors and physical-layer hardware |
Encrypting data before transmission | Security protocols such as IPsec or TLS |
Result — The control plane manages flow rules and makes the decisions about where traffic should go.