Software Defined Networking (SDN), is an emerging networking technology. This thesis aims to develop a new Server and Network Load balancing scheme in content delivery datacenters using SDN-based architecture. The scheme, called Server and Network Load Balancing (SNLB), tends to distribute the traffic load more evenly across the network. The SNLB achieves even distribution of flows on the links and servers by utilizing real-time network statistics. Furthermore, SNLB classifies the network flows into mice (flows with small bandwidth) and elephant (flows with large bandwidth) flows and performs load balancing on these two classes of flows separately. A detailed comparison of SNLB with Global first fit, Round robin and Load based balancing is presented. Other objectives achieved in this thesis are the designs of overload traffic handling technique and Fault tolerance method. The overload traffic handling technique activates and de-activates servers according to the traffic load; the fault tolerance method can reduce the impact on network performance during the network fault.