Neutron (Quantum) has some differences
Neutron is able to virtualize both the 2nd (logical) and 3rd (network) level of the OSI network model, as compared to simple 3rd level virtualization of nova-network.
This is the main difference between the two networking models for OpenStack.
Virtual networks (one or more) can be created for a single tenant, forming an isolated L2 network called a "private network."
Each private network can support one or many IP subnets.
Private networks can be segmented using two different technologies: