SDN: How the controller can get the installed flows on switch?

Question

According to described here http://flowgrammable.org/sdn/openflow/message-layer/flowmod/ and in the OpenFlow switch specifications, the flow_mod message is not acknowledgeable.

Is there any way for the controller (POX, ODL, or any other) to receive a confirmation for installed flow match or to retrieve the installed flows in the switch's flow table?

Thank you

Answer 1

There is a concept in openflow called "barrier" where the controller can send a barrier request to have the switch acknowledge the flow_mod.

In OpenDaylight, the default openflowplugin stats collection will poll the connected switches and will store the config (including the flow table) in OpenDaylight's operational store.