Open vSwitch

For the uninitiated, Open vSwitch is a production quality, multilayer virtual switch licensed under the open source Apache 2.0 license.  It is designed to enable massive network automation through programmatic extension, while still supporting standard management interfaces and protocols (e.g. NetFlow, sFlow, IPFIX, RSPAN, CLI, LACP, 802.1ag).  In addition, it is designed to support distribution across multiple physical servers similar to VMware’s vDS or Cisco’s Nexus 1000V. See full feature list here

For more information on OVS, I encourage you to check out the OVS website

https://communities.vmware.com/servlet/JiveServlet/previewBody/27611-102-2-37003/NSX-MH-DesignGuidev4.2_Final.pdf