Neutron (formerly Quantum) is a virtual network service for Openstack.

Just like OpenStack Nova provides an API to dynamically request and configure virtual servers, Neutron provides an API to dynamically request and configure virtual networks. These networks connect "interfaces" from other OpenStack services (e.g., vNICs from Nova VMs). The Neutron API supports extensions to provide advanced network capabilities (e.g., QoS, ACLs, network monitoring, etc)