OpenVirteX is a network hypervisor developed from 2013 to 2015 by OpenNetworkingLab, the same team that developed FlowVisor in the first place.
Although multiple additional features make OVX a larger project than the initial FlowVisor, OVX main feature is still to create multiple virtual SDN on top of a single infrastructure, by adding a virtualization layer between OpenFlow switches and SDN controllers[1].
As OVX is not being maintained anymore either, it also suffers from several defects, among which, the fact OVX uses OpenFlowJ, which doesn’t support most recent versions of OpenFlow (OF 1.3 is supported by OpenFlow J, but apparently not by OVX).
Yet, OVX is being used in research networks[2] and is preferable over FlowVisor for security concerns, but requires more physical resources for sometimes unnecessary features.
OpenNetworkingLab was further acquired by the Open Networking Foundation in 2017. The ON.Lab team is now working to take their work from FlowVisor and OpenVirteX to the ONOS project in order to add virtualization support the ONOS SDN controller.
[1]. OpenVirteX: Make Your Virtual SDNs Programmable, 2014, by Ali Al-Shabibi, Marc De Leenheer, Ayaka Koshibe, Guru Parulkar and Bill Snow. [2]. An Intent-based Network Virtualization Platform for SDN, 2016, by Yoonseon Han, Jian Li, Doan Hoang, Jae-Hyoung Yoo, and James Won-Ki Hong.