“Public cloud” or “Cloud computing” is a model of delivering Hosted Services provided by Service Providers over the internet. Service provider makes resources, such as virtual machines (VMs), applications or storage, available to the general public over the internet. Public Cloud providers have a multi-tenant architecture that enables users or tenants to share computing resources. Each tenant's data in the public cloud, however, remains isolated from other tenants. In public clouds although the resources are shared between multiple clients but all the services are controlled by services provider. Organizations that are fully dependent on IT to meet business goals have understood the value of cloud computing for its availability, scalability, instant provisioning, virtualized resources and storage. Public cloud architecture can be further categorized by service model. Common service models include:
Software as a service (SaaS)
A third-party Service provider hosts applications and makes them available to customers over the internet.
Platform as a service (PaaS)
A third-party Service provider delivers hardware and software tools usually needed for application development to its users as a service.
Infrastructure as a service (IaaS)
A third-party Service provider offers virtualized computing resources such as VMs and storage over the internet.