Southbound API control plane traffic between the SDN controller and SDN-enabled network elements must be mutually authenticated using a FIPS-approved message authentication code algorithm.

Southbound APIs such as OpenFlow provide the forwarding tables to network devices such as switches and routers, both physical and virtual (hypervisor-based). The SDN controllers use the concept of flows to identify network traffic based on predefined rules that can be statically or dynamically programmed by the SDN control software, thereby determining how traffic should flow through network devices based on usage patterns, applications, and policy that can optimize traffic paths based on business requirements and not network infrastructure design. If an SDN-aware router or switch received erroneous forwarding information from a rogue controller, traffic could be black-holed or even forwarded to a malicious user to sniff traffic and perform a man-in-the-middle attack. Hence, it is imperative that mutual authentication is enabled between the SDN controller and the SDN-aware network elements for all southbound API traffic.