Which are two open-source SDN controllers? (Choose two)

Big Cloud Fabric is a commercial SDN fabric solution developed by Big Switch Networks (now part of Arista Networks), not an open-source project.

OpenContrail (now Tungsten Fabric under the Linux Foundation) is an open-source network virtualization and SDN platform originally developed by Juniper Networks and released to the community under an Apache 2.0 license. It provides SDN control plane and network virtualization capabilities freely available to anyone.

Application Policy Infrastructure Controller (APIC) is Cisco's proprietary SDN controller used exclusively with its Application Centric Infrastructure (ACI) platform.

Virtual Application Networks SDN controller is a proprietary HP product and is not distributed as open-source software.

OpenDaylight is a major open-source SDN controller platform hosted by the Linux Foundation, providing a modular and extensible framework that supports multiple southbound protocols such as OpenFlow and NETCONF. It is community-driven and freely available, making it one of the most widely referenced open-source SDN controllers.