Packet-in messages are sent from the switch to the controller to transfer a packet received from one of the switch ports to the controller for further processing.
There are three ways in which the switch can send a packet-in event to the controller:
- Table-miss entry. When there is no matching flow entry for the incoming packet, the switch can send the packet to the controller. Refer to the Sending a switch configuration message to the switch recipe in Chapter 1, OpenFlow Channel Connection Establishment (Part 2), for the switch configuration required to send a table-miss packet to the controller.
- TTL checking. After decrementing the TTL value in the packet, and if the TTL value reaches zero, the switch can send the packet to the controller. Refer to the Sending a switch configuration message to the switch recipe in Chapter 1, OpenFlow Channel Connection Establishment (Part 2), for the switch configuration required to...