An overlay network uses tunneling technologies. Overlay networks are logical networks that are built on top of an existing physical network. They use tunneling technologies to encapsulate packets of one protocol inside packets of another protocol for the purposes of network virtualization, multitenancy, and more.

AppFormix gathers performance metrics in a network from an agent on a host or system. This allows it to directly monitor and collect data from the underlying infrastructure components, providing detailed and accurate performance insights.

NorthStar Planner is the product used to perform capacity planning on MPLS WANs. It specifically provides tools for network modeling, simulation, and optimization, which are essential for efficient capacity planning. Other options like Contrail Cloud, Cloud Service Orchestrator, and VMware NSX are not designed for this specific purpose.

To remove a node from the network for maintenance purposes and compute and provision alternate forwarding paths to re-route traffic around the affected node, you would use the maintenance mode feature of the NorthStar Controller. Maintenance mode is specifically designed to handle scenarios where nodes or links need to be taken offline for maintenance while ensuring minimal disruption to network traffic by precomputing alternate paths.

The SDN controller having a centralized view of the network is a fundamental characteristic of Software-Defined Networking (SDN). This centralized approach allows for superior network management and optimization, as the controller can make informed decisions based on a comprehensive overview of the entire network.