In Arno release, OpenDaylight Helium (SDN Controller) handled the layer 2 and overlay management of the network, while Neutron L3 agent handled routing. In OpenDaylight Lithium, a feature was added to do L3 routing and eliminates the need to use Neutron L3 agent.
This is a proposal to require Installers to support the ability to enable L3 routing functionality in the SDN Controller (where possible). Some SDN controllers may not support this functionality, in which case it is acceptable to use Neutron L3 agent.
OpenDaylight also supports distributed virtual routing (DVR). This requirement also proposes that Installers should be capable of enabling DVR on SDN controllers which support DVR.