In terms of switches: https://www.openstack.org/assets/survey/April-2016-User-Survey-Report.pdf - page 41 shows the neutron drivers. OVS tops the list and is just deployed with a Normal action on the switch.
There's also a benchmarking project called shaker http://shaker-docs.readthedocs.io/en/latest/ what's interesting there is the deployment scenarios http://shaker-docs.readthedocs.io/en/latest/examples/index.html

For Release D a version of the L2 Same Domain test is to be implemented at a stretch. A stretch because parallel VM scenario would be easier to start with. Then if we can we can enhance it fully into http://shaker-docs.readthedocs.io/en/latest/examples/full_l2.html#scenario