- Infrastructure-as-a-Service (IaaS)
- Platform-as-a-Service (PaaS)
- Software-as-a-Service (SaaS)
Infrastructure-as-a-Service (IaaS), also formerly called hardware-as-a-Service and that the similarity with the networks of electricity, water and gas, is sometimes referred to as utility computing, the final user creates one or more virtual machines, to all intents and purposes identical to those that are hosted in the server room.
Virtual machines that are activated and delivered virtually with an IP address of reference, have the characteristics required by the user: number of CPU, type and version of system OS, RAM, network cards, Internet access, disk space, etc..
The Platform-as-a-Service (PaaS), adds to a series of previous paradigm tool for the development and implementation of custom applications (Platform). Developers create these applications by using Application Programming Interface (API) portals and gateways and perform them on the same systems. Force.com, Microsoft Azure and Google Apps Engine PaaS offerings are some of the most common.
The model Software-as-a-Service (SaaS), allows the service provider to use complete a specialized software application and make it available, with the appropriate configurations, through a web portal. SaaS has a very wide applicability: the applications can be any service, by mail webbased, the management of stores, sales force automation, ERP.