Packet-out (OFPT_PACKET_OUT
) messages are sent from the controller to the switch when the controller wishes to send a packet through the switch data path via a switch port.
There are two ways by which the controller can send packet-out message to the switch:
- Construct the full packet. In this case, the controller generates the complete packet and adds an action list field in the
packet-out
message. Theaction
field contains a list of actions defining how the packet should be processed by the switch. It may include packet modification, group processing, and an output port. It can also specify theOFPP_TABLE
reserved port as an output action to process the packet through the OpenFlow pipeline. - Use a packet buffer in the switch. In this mechanism, the controller uses the buffer that was created at the time of sending the
packet-in
message to the controller by the switch. While sending thepacket_in
message to the controller, the switch adds thebuffer_id...