OVN provides network virtualization to containers. OVN's integration with containers works in two modes - the "underlay" mode or the "overlay" mode.
In the "underlay" mode, OVN requires a OpenStack setup to provide container networking. In this mode, one can create logical networks and can have containers running inside VMs, VMs and physical machines connected to the same logical network. This is a multi-tenant, multi-host solution.
In the "overlay" mode, OVN can create a logical network amongst containers running on multiple hosts. This is a single-tenant (extendable to multi-tenants depending on the security characteristics of the workloads), multi-host solution. In this mode, you do not need a pre-created OpenStack setup.
For both the modes to work, a user has to install Open vSwitch in each VM/host that he plans to run his containers.
For integration of OVN with Docker's libnetwork, read INSTALL.Docker.md
For backend tools that works independently of Docker's libnetwork, read backend.md
Once Docker provides the CLI to integrate with libnetwork, we plan to make the necessary changes to the ovn driver and get the code reviewed and added to the official Open vSwitch repo. Till then, any questions or discussions can be had at: discuss@openvswitch.org