Chapter 4. How does OpenDaylight cooperate with OpenStack?

OpenStack Networking (neutron) supports a plugin model that allows it to integrate with multiple different systems in order to implement networking capabilities for OpenStack.

For the purpose of OpenStack integration, OpenDaylight exposes a single common northbound service, which is implemented by the Neutron Northbound component. The exposed API matches exactly the REST API of neutron. This common service allows multiple neutron providers to exist in OpenDaylight. As mentioned before, the Red Hat OpenDaylight solution is based on NetVirt as a neutron provider for OpenStack. It is important to highlight that NetVirt consumes the neutron API, rather than replacing or changing it.

The OpenDaylight plug-in for OpenStack neutron is called networking-odl, and is responsible for passing the OpenStack network configuration into the OpenDaylight controller. The communication between OpenStack and OpenDaylight is done using the public REST APIs. This model simplifies the implementation on the OpenStack side, because it offloads all networking tasks onto OpenDaylight, which diminishes the processing burden for OpenStack.

Figure 4.1. OpenStack and OpenDaylight Architecture

The OpenDaylight controller uses NetVirt, then configures Open vSwitch instances (which use the OpenFlow and OVSDB protocols), and provides the necessary networking environment. This includes layer 2 networking, IP routing, security groups, and so on. The OpenDaylight controller can maintain the necessary isolation among different tenants.

In addition, NetVirt is also able to control hardware gateways using the OVSDB protocol. A hardware gateway is typically a top of rack (ToR) Ethernet switch, that supports the OVSDB hardware_vtep scheme, and can be used to connect virtual machines with the actual physical devices.