The technology industry is notorious for its love of acronyms, particularly when it comes to cloud computing. With cloud-based solutions becoming increasingly essential for every company and industry worldwide, three key cloud service models have emerged as the backbone of the cloud revolution: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS). The phrase “as-a-Service” refers to a wide variety of technology services delivered to companies or individuals via the internet by a third-party service provider.


All three major cloud computing models — also known as the cloud computing stack — offer a layer of abstraction to users building or consuming application systems. The service provider’s responsibility is to set up and manage the services, allowing companies to focus on taking advantage of their IT solutions to serve their customers instead of using valuable time and resources to maintain technology.

This article examines the three primary layers of the cloud computing stack and explains each model’s benefits and how they come together to create a total computing environment for corporate needs.


As its name implies, this service is the infrastructure layer of the cloud stack. With IaaS, a service provider can provide your company with a robust, cloud-based alternative to hosting on-premises infrastructure, saving companies from investing in costly on-site resources.

With the IaaS computing model, users can — manually or via automated API and console solutions — provision infrastructure for various uses. You may use your cloud infrastructure resources for data repositories and other storage, security services, networks, computing instances, and other vital utilities like backups. What’s more is that you can use the infrastructure to deploy bespoke software solutions, operating systems, or a range of off-the-shelf applications.

As the user, your company manages and controls everything within the stack above the operating system layer, such as operating systems, runtime, applications, data, security, and governance. Your IaaS solution provider then takes care of servers, hard drives, networking, storage, and virtualization.

This model gives your company the flexibility to invest in only the virtual hardware components that you need and lets you scale down or up as required. Because of low overheads and no hardware maintenance, IaaS offers you affordable business computing regardless of your company’s size.

Some of the situations that suit the use of cloud-based infrastructure include periods of volatile demand on your infrastructure or if your organization is new and does not have investment capital. Examples of IaaS are Rackspace, Google Compute Engine, Microsoft Azure, and Amazon Web Services EC2.

However, an infrastructure without any systems running on it is as useless as a highway without any cars driving on it, so this is where PaaS comes in.


Enterprise PaaS solutions give your vendors or line-of-business developers a convenient way to manage computing infrastructure. In keeping with our highway analogy above, think of the infrastructure layer as the road and the platform layer as the cars driving on the road.

Platform-as-a-Service exposes the cloud application layer that sits on your IaaS stack, allowing your company to develop and deploy on virtualized servers and use the infrastructure layer’s networking and storage capacity. The platform layer of the cloud application stack offers a development- and deployment-ready environment that includes operating system software development frameworks, dev tools, and application programming interfaces like Python, .NET, and Java. This model also gives you access to business analytics and database management systems.

As a PaaS consumer, you are only responsible for building and deploying your cloud applications. The service provider handles the application stack and the infrastructure hosting your application development platforms. With the increase in remote working arrangements today, PaaS offers your developers the unique opportunity to perform their jobs no matter where they are.

Examples of PaaS in action are Heroku, Pivotal Cloud Foundry, AppScale, Amazon Web Services Elastic Beanstalk, and RedHat OpenShift Container.

Returning to our highway example, it’s clear we now have a highway and cars, but no one to ride in the vehicles, which means we must introduce the top layer of the three-tiered stack: the software layer.


Software-as-a-Service solutions are some of the most common computing products that companies use for building and growing their businesses.

SaaS represents the world’s largest cloud market and is rapidly expanding every day. Through the internet, a service provider can offer your company fully-managed applications with client interfaces that you can access via your web browser. Among the most popular SaaS business solutions are email, collaboration suites, healthcare solutions, and Customer Relationship Management (CRM) systems.

Most applications in this layer of the cloud stack do not need you to download or install them locally, though some of them might require plugins to work correctly. To access your applications and start using them, all you need is to supply some credentials to log in.

The most significant advantage of using SaaS is that solutions are often straightforward to set up and manage. Additionally, SaaS products are highly scalable. You can quickly deploy a solution to your entire company or team — an especially crucial feature when you have a company with distributed teams.

SaaS applications are easy to get started with because they are built upon an entire stack of managed cloud systems — including the infrastructure and platform layers. You do not need to host physical servers on your premises, manage any platforms or OSes, or even do much development. You access a solution that is — for all intents and purposes — ready to use “out of the box.”

Mainstream examples of Software-as-a-Service include Cisco WebEx, Concur, Citrix GoToMeeting, Google Apps, Salesforce, Workday, and Microsoft 365. Another example for Software-as-a-Service is the hosted and penetration-testedversion of Access Capture


With an understanding of how the cloud computing stack works together, it is crucial to examine how closely it parallels traditional application hosting. In the past, most organizations hosted all the software and applications they used within their in-house physical infrastructure — hardware, servers, and data centers. All the software that users required sat on a programming environment or OS residing within a physical infrastructure.

Today, the cloud provides you with a relatable infrastructure-platform-software stack. In practice, network admins and systems architects build your business’ technology systems on IaaS. PaaS — built on this infrastructure — then gives development teams the environment they need to deploy your applications. Finally, SaaS is a managed environment that contains all the applications that your employees use to carry out their daily tasks.

Capture software as a service Penetration tested, for larger enterprises

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