In designing a lab using Open vSwitch, I quickly found that this excellent virtual switch with vlan, vxlan, gre tunnels, and open flow support, has terse documentation. Also, due to rapid development, a great deal of the blog based documentation is out of date.
Scott Lowe has posted many articles on KVM/OVS which I have found to be the most useful documentation source (although some also out of date), so I recommend you check out his blog.
He also wrote a nice piece on why this (SDN/OVS) is rapidly becoming important. Basically, they are aimed at solving the issues we have incorrectly been throwing VLAN at.
http://blog.scottlowe.org/2013/06/20/thinking-out-loud-the-future-of-vlans/
All your cloud are belong to us 