Home > Articles

How the Internet Works: The Layers of the Cloud

IaaS, PaaS, SaaS: Learn the definitions and differences of the three layers of Cloud computing.
Like this article? We recommend

Too often, the vast majority of online articles and blogs concerning the Cloud talk about the technology through the guise of generalization, as if saying "the Cloud" multiple times succinctly and clearly explained everything about "the Cloud."

Well, as a believer in the more knowledge you have the better, below is a quick starter course in Cloud education aimed at peeling back the layers of "Cloud computing" to introduce you to SaaS, PaaS, and IaaS. In this entry of "How the Internet Works," the Cloud is broken down into its core elements.

Like an onion, the Cloud has layers. Not just made up of catchy marketing terms and lingo which goes out of its way to remain obtuse, Cloud computing is comprised of three major layers: SaaS, PaaS and IaaS. Of the three, IaaS is the foundation; SaaS is the top layer, functioning off both PaaS and IaaS. Interestingly enough, although SaaS is normally represented in graphics as the smallest layer of Cloud infrastructure, it is anything but.

In this installment of "How the Internet Works" I will explain, from the foundation up, what the layers of the Cloud accomplish and how each respective layer—IaaS, PaaS, SaaS—operates/feeds into one another.

IaaS: Infrastructure as a Service

IaaS, or Infrastructure as a Service, refers to the hardware, network equipment, and web hosting servers which web hosting companies rent out to consumers. The IaaS layer of Cloud computing is comprised of all the hardware needed to make Cloud computing possible. Used day in and day out by network architects (sometimes called NOCs) and web hosting professionals, the IaaS layer is the physical foundation of Cloud Computing which can be and is leased out to users to run their own Cloud-based services.

The IaaS layer of Cloud Computing is physical hardware. Regardless of what anyone tells you, the Cloud is based on physical computing hardware (servers, nodes, PDUs, blades, hypervisors, cooling gear, etc.) stored in a data center (also called a DC) operated by network architects, network engineers, and web hosting professionals/companies. The big takeaway here: The Cloud is physical, and without the IaaS layer, neither PaaS nor SaaS would be possible.

PaaS: Platform as a Service

PaaS, or Platform as a Service, refers to the middle layer of the Cloud used for development by web developers, programmers, and coders. The PaaS layer of the Cloud is used to create applications, programs, software, and web tools. PaaS works by developers renting raw hardware from an IaaS provider, which can then be used as the platform to build software, applications, programs and web tools.

In most cases, developers will purchase the PaaS layer of the Cloud from infrastructure providers like RackSpace, Amazon EC2, Linode, Digital Ocean, and the like. The purchased infrastructure will come with pre-installled developer tools like Apache, MySQL, Ruby, LAMP Stack, Dokku, and GitLab.

The majority of providers sell PaaS-level servers to consumers on a per-resource allocation. Whereas you might purchase a car with 255 horsepower, leather seats, and heated rear-view mirrors, developers will purchase a Cloud server with a specific allotment of RAM, disk space, CPU cores and bandwidth. A typical Cloud server might look like 4GB of RAM, 60GB of disk space, 4 CPU cores and 8TB of bandwidth.

The big takeaway here: The PaaS layer of the Cloud is based on the IaaS layer of the Cloud, and is used to build the highest layer of the Cloud, SaaS applications.

SaaS: Software as a Service

SaaS, or Software as a Service, is the topmost layer of the Cloud. SaaS serves as the layer of the Cloud which the vast majority of consumers use. Built on top of both IaaS and PaaS, Software as a Service provides applications, programs, software, and web tools to the public for free or for a price. Accessible via a computer, tablet, or smartphone, the SaaS layer of the Cloud encompasses the largest and most accessible layer of Cloud computing.

Every time you use the Google Play Store, iOS App Store, Dropbox, Salesforce, Adobe Cloud Suite, Spotify, or any other Cloud-based software which is stored in a web server located in a data center halfway around the world, you are accessing the SaaS layer of the Cloud.

As alluded to, the basic premise of SaaS is user-friendly software, accessed via a computing device of choice, and stored on a server. A perfect example of SaaS is Microsoft Office 365. Without Microsoft Office 365, a company would be forced to:

  • Purchase individual copies of software or software bundles, driving up per-seat cost
  • Worry about per-seat software upkeep
  • Purchase new versions of software based on a per-seat basis

With SaaS-enabled Microsoft Office 365:

  • SaaS eliminates per-seat software purchases. Companies purchase/rent a license to utilize a single version of the software in question which is stored, maintained, and updated on a central server.
  • SaaS eliminates the need for software maintenance, upkeep, or upgrade. As the software is hosted by a parent company, the parent company updates the software, and that update filters down the line automatically.
  • SaaS is scalable. Without SaaS, a company continually purchases new copies of software for new employees. With SaaS, a company rents the license to the software from the hosting company. With new employees, the software license is scaled to meet demand.

The big takeaway here: The SaaS layer of the Cloud is based on both the IaaS and PaaS layers of the Cloud, and is used to provide applications to the market at a lower cost and with a lower local hardware resource need. SaaS is scalable, more affordable, and easier to maintain than traditional software bundles.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020