When ODL is connected to ovs 2.8 version switch, default openflow protocol version is not set, due to which handhshaking is not completed.

OVS2.8 and above communicates with OF 1.4 protocol by default. Hello message sent by OVS2.8 will have version set as OF 1.4 without bitmap. When switch sends hello message without bitmap and the version set is higher than the controller supported version, controller will send HELLO message with the bitmap containing list of controller supported OF versions (OF1.3, OF1.0). Once, ovs receives this HELLO message, it is negotiating the higher supported common version available in the bitmap. From then on OVS will send openflow messages with version set as 1.3. When the HELLO message sent by controller is successful, it should go to the post handshake steps, instead of waiting for next HELLO message from switch.