Software-defined network (SDN)
Q7. Which of the following are true about SDN Controller? (Choose 2 best answers)
A. Manages flow control to the switches/routers ‘below’ (via southbound APIs)
B. Manages applications and business logic ‘above’ (via northbound APIs) to deploy intelligent networks.
C. OpenFlow is used to communicate with the networking devices via southbound APIs
D. It is used to collect information about networking devices using SNMP.
Correct Answer: A, B
SDN Controllers in a software-defined network (SDN) are the 'brain' of the network. It is the application that acts as the control point in the SDN network, manage flow control to the switches/routers 'below' (via southbound APIs) and the applications and business logic 'above' (via northbound APIs) to deploy intelligent networks.
An SDN Controller platform contains a collection of "pluggable" modules that can perform different network tasks. Some of the basic tasks including inventorying what devices are within the network and the capabilities of each, gathering network statistics, etc. Extensions can be inserted that enhance the functionality and support more advanced capabilities, such as running algorithms to perform analytics and orchestrating new rules throughout the network.
Two of the most well-known protocols used by SDN Controllers to communicate with the switches/routers is OpenFlow and OVSDB. Others protocols that could be used by an SDN Controller is YANG or NetConf.
Note that OpenFlow is used to communicate with the applications and services via Northbound APIs.
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