Asterisk includes the concepts of Device State , Extension State and Presence State which together allow Asterisk applications and interfaces to receive information about the state of devices, extensions and the users of the devices. Additionally, modules exist for Corosync and XMPP PubSub support to allow device state shared and distributed across multiple systems.
The sub-sections here describe these concepts, point to related module specific configuration sections and discuss Querying and Manipulating State information.
