Open vSwitch is an open-source virtual switch software designed for virtual servers. The role of this software is to forward traffic between different virtual machines (VM) within the same host and even traffic between a VM and a physical network. This supports standard management interfaces like NetFlow, sFlow, CLI and RSPAN. Open vSwitch can accept program extensions and control using OpenFLow, as well as make use of the OVSDB management protocol.
Techopedia explains Open vSwitch
Open vSwitch is designed to be compatible with modern switching chipsets so that it can be ported to high-fanout switches, thus providing the same flexibility of control to physical infrastructure as virtual ones.
Open vSwitch is able to run on any Linux-based virtualization platform with a kernel of 2.6.18 or later. These platforms are VirtualBox, KVM, Xen, XenServer and the Xen Cloud Platform. Open vSwitch is written in C and can be ported to any environment. As of Linux 3.3, it is part of the mainline kernel.