1.3: “Everything-as-a-Service” Models- IaaS, PaaS, SaaS and Beyond

A fundamental concept of cloud computing is the idea of delivering “Everything as a Service” (XaaS). Rather than purchasing technology assets, organizations can subscribe to technology solutions as services on-demand. This model originated with core service categories – Infrastructure, Platform, and Software – and has expanded to encompass a wide range of offerings. The XaaS approach turns computing into a utility: virtually any IT function can be abstracted and provided by a third-party service over the network.

In this section, we explain the main service models – Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) – and touch on further extensions of the XaaS paradigm. Understanding these models is critical for businesses to choose the right mix of services for their needs and to appreciate the differing levels of control vs. convenience each model offers.

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