Cloud Models & Cloud Service Providers | CompTIA Security+ SY0-601 | 2.2a

In this video you will learn about cloud models such as: IaaS, PaaS, SaaS, & XaaS. You’ll also learn about various cloud delivery models such as: private clouds, public clouds, hybrid clouds, & community clouds.

Cloud Computing

Cloud computing is the on-demand availability of computer system resources, especially data storage and computing power, without direct active management by the user.[1]  Large clouds often have functions distributed over multiple locations, each location being a data center.  Cloud computing relies on sharing of resources to achieve coherence and typically using a “pay-as-you-go” model which can help in reducing capital expenses but may also lead to unexpected operating expenses for unaware users.[2]

IaaS (Infrastructure-as-a-Service)

IaaS, also known as cloud infrastructure services, is a form of cloud computing in which IT infrastructure is provided to end users through the internet.  IaaS is commonly associated with serverless computing.  The IaaS vendor provides the virtualization, storage, network, servers, and allows for customers to utilize/pay for virtual resources when they are needed.  This cloud computing model allows for customers to not have to have an on-premise datacenter and not worry about physically updating or maintaining these components themselves.  Most importantly, this model allows for companies to reduce the costs of their network infrastructure by outsourcing storage & computing services to a cloud provider.  IaaS puts users in charge of all the software used in a project, from applications and data to the operating system.  IaaS vendors supply the hardware and network support tools.  The three largest cloud providers at the time of this writing are:

  • Amazon Web Services (AWS)
  • Microsoft Azure
  • IBM

PaaS (Platform-as-a-Service)

PaaS is a category of cloud computing services that provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app.  A developer using PaaS can concentrate on software features instead of possible issues with server hardware and operating systems.  Some of the major PaaS vendors include:

  • Oracle Cloud
  • Google Cloud Platform
  • Microsoft Azure
  • Salesforce Platform

SaaS (Software-as-a-Service)

SaaS is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted.  SaaS applications are also known as web-based software, on-demand software and hosted software.  Because SaaS processing is performed at the server, a thin client, smartphone, or tablet is sufficient to run the software.  A browser-based service that does not require a user to download application code to use the service is an example of SaaS.  SaaS allows organizations to get quickly up and running without having to develop or deploy an application.  Examples of SaaS applications are:

  • Gmail:  provides access to email services via Google.
  • Google Drive:  provides access to word processing, spreadsheets, presentations, & various other forms.
  • Microsoft Office 365:  provides access to word processing, spreadsheets, presentations, calendars, email, etc.
  • Salesforce:  a customer relationship management application.

XaaS (Anything-as-a-Service)

XaaS is a term that describes a broad category of services related to cloud computing & remote access.  With cloud computing technologies, vendors offer companies different kinds of services over the web or similar networks.  This idea started with the basic SaaS (software-as-a-service) with cloud providers offering individual software applications.  Other terms like IaaS (infrastructure-as-a-service) & CaaS (communications-as-a-service) were added as cloud services evolved.  The core idea behind XaaS and other cloud services is that businesses can cut costs & get specific kinds of personal resources by purchasing services from providers on a subscription basis.  With XaaS, businesses simply buy what they need and pay for it as they utilize it.[3]

Cloud Delivery Models

Cloud computing comes in four general categories:

  • Private Cloud:  Defined as computing services offered over the Internet or a private internal network & only to select users instead of the general public.  Private cloud computing is considered to be more secure than public cloud computing.
  • Public Cloud:  Defined as computing services offered by 3rd-party providers over the public Internet, making them available to anyone who wants to use or purchase them.  They may be free or sold on-demand, allowing customers to pay only per usage for the CPU cycles, storage, or bandwidth they consume.
  • Hybrid Cloud:  A computing environment that combines public cloud & a private cloud by allowing data and applications to be shared between them.  When computing and processing demand fluctuates, hybrid cloud computing gives organizations the ability to seamlessly scale their on-premises infrastructure up to the public cloud to handle any overflow — without giving 3rd-party data centers access to the entirety of their data.
  • Community Cloud:  A collaborative effort in which infrastructure is shared between several organizations from a specific community with common concerns (security, compliance, jurisdiction, etc), whether managed internally or by a 3rd-party and hosted internally or externally.  This is controlled and used by a group of organizations that have shared interest.  The costs are spread over fewer users than a public cloud (but more than a private cloud), so only some of the cost savings potential of cloud computing are realized.


  1. Montazeroghaem, A.; Yaghmaee, M.H.; Leon-Garcia, A. (2020). Green Cloud Multimedia Networking: NFV/SDN Based Energy-Efficient Resource Allocation. IEEE.
  2. Wray, J. (2014). Where’s The Rub: Cloud Computing’s Hidden Costs. Forbes.
  3. (2017). Anything as a Service (XaaS): What Does Anything as a Service (XaaS) Mean? Techopedia.