Apart from the main connection, a switch can initiate one or more connections towards the controller to improve switch processing performance and exploit the parallelism of most switch implementations. These connections are termed auxiliary connections. The controller should recognize incoming connections with a non-zero Auxiliary ID as auxiliary connections and bind them to the main connection with the same Datapath ID. The Datapath ID of the main connection and the auxiliary connection is the same; this helps the controller to bind the auxiliary connection to the main connection.
The controller should not accept an auxiliary connection from the switch until the main connection is successfully established.