Asynchronous messages

Asynchronous messages are initiated by the switch and are used to update the controller of network events and changes to the switch state. Switches send asynchronous messages to the controller in order to denote a packet arrival, switch state change, or an error. There are seven main asynchronous messages, as follows:

• Packet-in
• Flow-Removal
• Port-status
• Controller-status
• Table-status
• Request-forward