This section presents the objects and semantics of Quantum’s logical model.
Quantum abstracts the physical implementation of the network, allowing plugins to configure and manage physical resources. Quantum is a standalone service, in that it requires no other project within OpenStack to function correctly.
Further Quantum is agnostic to the entities it allows to connect. While we anticipate Nova instances will be a heavy user of Quantum, any entity can make use of any Quantum created network so long as it provides an appropriate interfaces for exposing VIFs to Quantum itself.
Virtual Interfaces (VIF) in the logical model are analogous to physical network interface cards (NICs). VIFs are typically owned a managed by an external service; for instance when Quantum is used for building OpenStack networks, VIFs would be created, owned, and managed in Nova. VIFs are connected to Quantum networks via ports. A port is analogous to a port on a network switch, and it has an administrative state. Quantum API allows for controlling the administrative state of the port, which can be either 'DOWN' or 'ACTIVE'.
When a VIF is attached to a port the Quantum API creates an attachment object, which specifies the fact that a VIF with a given identifier is plugged into the port.
The Quantum plugin is responsible for managing virtual and/or physical network switches to implement the network forwarding connectivity described by the Quantum networks, ports, and attachments.
VIFs attached to ACTIVE ports are required to have access to the L2 broadcast domain defined by the network where they are attached. Each VIF shall be capable of exchanging traffic with all other entities attached through ACTIVE ports.
