Cloud Computing Service Models

There are three cloud service models.

1. Infrastructure as a Service (IaaS)
2. Platform as a Service (PaaS)
3. Software as a Service (SaaS).

Lets see in brief what each service model is.

1. Infrastructure as a Service (IaaS):

               IaaS model provides  Infrastructure such as servers, disk storage, networking etc as a service. Rather than purchasing physical infrastructure, the IaaS vendor provides infrastructure and manage and maintains the infrastructure for specified usage charges. Examples of IaaS vendors are Amazon Web Services (AWS), Rackspace and GoGrid.

    2. Platform as a Service (PaaS)

               What IaaS is to infrastructure PaaS is to applications. PaaS sits on top of

IaaS and abstracts much of the standard application stack–level functions and provides those functions as a service. Examples of PaaS vendors are Force.com, Google Apps Engine and Microsoft Azure. PaaS vendors dictates platform stack and underlying infrastructure. 

   3. Software as a Service (SaaS)
             SaaS is the complete application delivered as a service to the service consumer. The service consumer has to configure some application-specific parameters and manage users. Some very common SaaS applications are customer relation Management (CRM), enterprise resource planning (ERP) and payroll, accounting applications.