Cloud computing offers organizations new choices regarding how to run infrastructures, save costs, and delegate liabilities to third-party providers. It has become an integral part of technology and business models, and has forced businesses to adapt to new technology strategies. Accordingly, the demand for cloud computing has forced the development of new market offerings, representing various cloud service and delivery models. These models significantly expand the range of available options and task organizations with dilemmas over which cloud computing model to employ
Cloud service models describe how cloud services are available to clients. According to NIST, there are three service models: SaaS (Software as a Service), PaaS (platform as a Service and IaaS (Infrastructure as a Service) that are described in the following sections. In fact, most fundamental service models include a combination of IaaS, PaaS and SaaS. These service models may have synergies between each other and be interdependent; for example, PaaS is dependent on IaaS because application platforms require physical infrastructure.
Today, companies realize more value and resource-savings from software and platform services rather than infrastructure. Therefore IaaS service delivery model is likely to keep losing market share to PaaS and SaaS. It is expected that in the near future significant number of market consolidations with few large players retaining market control at the end [9].