SDN is an emerging networking paradigm that separates the network control plane from the data forwarding plane with the promise to dramatically improve network resource utilization, simplify network management, reduce operating costs, and promote innovation and evolution. While traffic engineering techniques have been widely exploited for ATM and IP/MPLS networks for performance optimization in the past, the promising SDN networks require novel traffic engineering solutions that can exploit the global network view, network status, and flow patterns/characteristics in order to achieve better traffic control and management. This article discusses the state-of-the-art in traffic engineering for SDN with attention to four cores including flow management, fault tolerance, topology update, and traffic analysis. Challenging issues for SDN traffic engineering solutions are discussed in detail.