The described embodiments provide techniques and architectures for enabling interoperability between legacy network systems and Software Defined Networking (SDN) systems. The embodiments add functionality to an SDN system to support interworking between an SDN controlled network, and a legacy network. When upgrading a legacy system to SDN, it may not be possible to upgrade all network components at once. The described embodiments facilitate the use of legacy network components together with SDN system components, by adding new functionality to the SDN data plane elements and control plane elements. The SDN forwarding network elements (NEs) terminate the physical links carrying legacy protocols that include combined data traffic and control information. The new functionality within the SDN forwarding NEs includes processing none or some of the control messages from a legacy NE within an SDN forwarding NE, and then forwarding the remaining control messages to the controller under which that particular SDN forwa
