Cloud Service Models
When you look deeper into what services can be provided by a cloud implementation, you start talking about cloud service models. The NIST definition of cloud computing outlines three basic service models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). We will briefly cover these models here, then cover them more in depth in a later chapter.
Infrastructure as a Service(IaaS)
Infrastructure as a Service, or IaaS, provides basic infrastructure services to customers. These services may include physical machines, virtual machines, networking, storage, or some combination of these. You are then able to build whatever you need on top of the managed infrastructure. IaaS implementations are used to replace internally managed datacenters. They allow organizations more flexibility but at a reduced cost.
Platform as a Service(PaaS)
Platform as a Service, or PaaS, provides an operating system, development platform, and/or a database platform. PaaS implementations allow organizations to develop applications without having to worry about building the infrastructure needed to support the development environment. However, depending on the PaaS implementation you go with, you may be limited in what tools you can use to build your applications.
Software as a Service(SaaS)
Software as a Service, or SaaS, provides application and data services. Applications, data, and all the necessary platforms and infrastructure are provided by the service provider. SaaS is the original cloud service model. It still remains the most popular model, offering by far the largest number of provider options.