OVN

OVN, short for Open Virtual Network, is an open-source project that provides a programmable, policy-driven virtual networking layer for cloud environments. Built on the Open vSwitch (OVS) ecosystem, OVN aims to decouple the control plane from the data plane, enabling scalable, multi-tenant networks for virtual machines and container workloads. It defines logical network abstractions that can span multiple hosts and can be managed independently of the underlying physical network.

The OVN architecture centers on a two-database model and a modular control plane. The Northbound database stores high-level network policies and topology information (such as logical switches, logical routers, and ports). The Southbound database holds a lower-level, platform-specific representation that is translated into OVS datapath flows. The northd daemon translates Northbound into Southbound, while an ovn-controller on each hypervisor programs the local OVS instance to realize the desired state. A central ovn-northd component orchestrates policy translation and ensures consistency across the deployment.

Key features of OVN include logical switching, logical routing (including distributed routing for scalability), NAT, ACL-based security policies, load balancing, DHCP, and QoS. The system can support distributed gateway functionality, multi-tenant isolation, and external connectivity through integrations with physical networks. OVN integrates with OpenStack via Neutron drivers and with Kubernetes through OVN-Kubernetes, enabling pod-level networking and policy enforcement.

OVN is maintained as an open-source project within the Open vSwitch ecosystem and is used in various private cloud and data center environments. Its design emphasizes scalable control of virtual networks while leveraging the performance of OVS for the data plane.