This document discusses network virtualization in OpenStack clouds. It acknowledges contributions from OpenStack community members and network engineers. It outlines how OpenStack's Quantum project allows networking to be treated as a first-class service. Quantum supports plug-ins for different virtual network implementations like Open vSwitch, NVGRE, and VXLAN. The document also describes the speaker's work on a virtual cube (vCube) network service that provides quality of service, visibility, and a transition between VLAN and GRE solutions in OpenStack clouds.