I. INTRODUCTION
Cloud computing is a computing model that maintains statistics and applications, using internet and central secluded servers. This methodology permits end users and businesses to use applications without putting in and entrée their private records at any computer with internet entrée. Cloud computing permits for much more proficient computing by centralizing storage, reminiscence, dispensation and bandwidth. Some examples of cloud computing are Yahoo email, Google, Gmail, or Hotmail etc. The server and email administration software is all on the cloud and is completely managed by the cloud service supplier. The end user gets to use the software unaccompanied and get pleasure from the benefits. Cloud computing acts as a service moderately than a merchandise, whereby mutual resources, software, and information are provided to computers and other strategies. Cloud computing can be categorized into three services [15]: i) SaaS (software-as-a-service), ii) PaaS (platform-as-a-service), iii) IaaS (infrastructure-as-a-service) respectively. Allocation of Cloud resources should not only guarantee Quality of Service (QoS) constraints specified by clients via Service Level Agreements (SLAs), but also to condense energy consumption.