The document discusses network service in OpenStack cloud. It introduces SDN and network virtualization technologies like OpenFlow, VXLAN, and NVGRE. It describes how OpenStack's Quantum project provides network as a service and supports various plug-ins for virtual and physical network provisioning, including options from Open vSwitch, NVP, Cisco, and OpenFlow controllers. It also outlines the speaker's work on a virtual network solution called vCube that enables coexistence of VLAN and GRE networks in OpenStack and provides QoS and visibility capabilities.