Cloud Infrastructure-as-a-Service (IaaS) is a form of utility computing which has emerged with the recent innovations in the service computing and data communication technologies. Regardless of the fact that IaaS is attractive for application service providers, satisfying user requests while ensuring cloud operational objectives is a complicated task that raises several resource management challenges. Among these challenges, limited controllability over network services delivered to cloud consumers is prominent in single datacenter cloud environments. In addition, the lack of seamless service migration and optimization, poor infrastructure utilization, and unavailability of efficient fault tolerant techniques are noteworthy challenges in geographically distributed datacenter clouds. Initially in this thesis, a datacenter resource management framework is presented to address the challenge of limited controllability over cloud network traffic. The proposed framework integrates network virtualization functionalities offered by software defined networking (SDN) into cloud ecosystem. To provide rich traffic control features to IaaS consumers, control plane virtualization capabilities offered by SDN have been employed. Secondly, a quality of service (QoS) aware seamless service migration and optimization framework has been proposed in the context of geo-distributed datacenters. Focus has been given to a mobile end-user scenario where frequent cloud service migrations are required to mitigate QoS violations. Finally, an SDN-based dynamic fault restoration scheme and a shared backup-based fault protection scheme have been proposed. The fault restoration has been achieved by introducing QoS-aware reactive and shared risk link group-aware proactive path computation algorithms. Shared backup protection has been achieved by optimizing virtual and backup link embedding through a novel integer linear programming approach. The proposed solutions significantly improve bandwidth utilization in inter-datacenter networks while recovering from substrate link failures.