Question

When does a switch send PAKCET-IN message to a controller in SDN
:

Answer 1

When a flow-rule associated with a received flow does not exist


Hope this helps :)

Answer 2

Answer:

When does a switch send PAKCET-IN message to a controller in SDN  Flow-rule associated with a received flow does not exist

Explanation:

• The Packet In message is the kind of process of send a captured packet from the switch to the controller node.  We make a Packet In message  process based on two reasons , like ;  matching the behavior of the simulation node , and also the mis-match data in the tables, or a TTL error occurred.
• The Packet In message consists of the following elements ,like , header, buffer id, which is the is a unique value for track the buffered packet, total_len , which is specify the length of the captured packet, in_port , which is used to port the packet was received on, reason, which is indicates , the reason for the packet has been captured and forwarded and also pad, which is captured portion of the packet starts.

Packet-in message transmission levels

• We can perform the packet-in message transmission in two different levels
• In the level one, we perform the process of  the switch hardware Sending a packet to the SDN controller. The process equal or  same as like sending a packet to any destination.  In this level the  switch can send Any addressed packet forwarded to the SDN controller and also forwards packets to any other destination. In this level we can install a rule into the switch  for forward a packet to the controller. if it is addressed to another destination then stop the rule based transmission.
• In the level two , the SWITCH Sending a packet itself and to the controller. The level two switching process is completed by the Switch’s CPU. In this process the switch will create a packet with the desired contents and set the SDN controller as the destination node.