With the increasing scale of the network, the traditional telecommunication network faces many challenges, and needs to be changed urgently in order to provide efficient and fase operation and maintenance methods, and reduce labor costs and OPEX expenses. -- The number and types of devices have increased dramatically. -- Huge online customers amount making it difficult to develop new services in existing resources. -- Existing network resources are complex, manual analysis takes a long time, and subject to errors. -- New technologies, new equipment, and new services are constantly emerging, and need higher skills of maintenance. SDN is an open, programmable network architecture with separated forwarding & control, and supports centralized management & control, open and programmable, on-demand and free migration of network functions, intelligent management of service life cycle and flexible system deployment. It is the mainstream trend for the future network.