ONOS (Open Network Operating System) focuses on carrier-grade performance and availability.
Design principles: Distributed from ground up, high availability, horizontal scaling, sub-second failover.
Architecture layers:
Distributed core. Manages cluster membership, leader election, state distribution.
Subsystems. Device, topology, flow, host, and intent managers.
Applications. Reactive forwarding, SDNIP for BGP peering, segment routing.
Cluster operation: Minimum instances for quorum. State replicates across nodes. Automatic leader election.
ONOS handles thousands of switches.