What Is Cloud Computing?

Cloud computing is one of those phrases that is often misunderstood and unfortunately has several—and sometimes conflicting—definitions. Some are quick to say it’s a buzzword that describes existing technologies, while others would rather debate the finer academic and scientific (and sometimes social) aspects, and still others insist cloud computing is the future of information technology.

Thus, some have flatly stated that cloud computing is nothing more than grid computing, while others suggest cloud computing could represent the entire Internet. Both views are flawed. Others will explain in detail all aspects of “as a service” concepts and use those to define cloud computing. Fortunately, these more nuanced views are much closer to the truth.

Cloud computing is essentially a remix of a group of technologies that include grid computing and virtualization combined with application programming interfaces (APIs) and utilities to supply access to the virtualized environments. In his book Cloud Computing Architectures, George Reese states, “There is nothing fundamentally new in any of the technologies that make up cloud computing.” This is a sobering observation that some pundits and marketers would rather not face. However, the advancement comes in the packaging, through which giants like Amazon have made it possible to use existing technologies in a whole new way.

In his treatise “15 Ways to Tell It’s Not Cloud Computing,” James Governor makes some strong statements concerning what is and what isn’t cloud computing. To paraphrase his arguments, Governor makes it clear that cloud computing isn’t something that takes a long time to explain, has a complex and steep learning curve, is isolated or requires a dedicated connection to use, or requires you to purchase hardware. Whether you agree with him or not, he forces patrons of companies trying to rebadge their products with the word “cloud” in them to consider their purchases carefully because the cloud isn’t what most people think it is.

The term “cloud computing” is derived from the conceptual drawing that depicts resources hosted in a large network (a cloud). We use a cloud symbol because the resource implementation (e.g., the hardware, operating system, etc.) is hidden and has little bearing on what the service is or what it provides—it is simply a service you can use. Thus, instead of seeing gateways, routers, and servers, you see the resources presented as a service. Consumers of the resources don’t care how the service is implemented; of overarching importance is for the service to solve the need and be available when required.

Rather than say “cloud computing is many things to many people,” the National Institute of Standards and Technology (NIST) defines cloud computing as follows:

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The characteristics that most cloud researchers define as essential to cloud computing include the following:

On-demand self-service
Customers can pick and choose what they need on an ad hoc basis without intervention of the vendor or a third party.

Broad network access
The resources are available through existing networking capabilities.

Resource pooling
Multiple users share the provider’s hardware (e.g., a multitenant sharing model).

Rapid elasticity
Customers are able to rapidly scale resources either manually or automatically.

Measured service
Services for resource monitoring and management are provided, either actively or passively.

The three service models are:

Infrastructure as a Service (IaaS)
Resources are provided as virtual instances of complete hardware or operating system platforms. The client can add virtualized computational resources on demand (e.g., servers, load balancers). Thus, the components of an information infrastructure are provided as components or middleware. The consumer has access to and control of the resources (e.g., the customer can manage an allocated server).

Platform as a Service (PaaS)
An API allows clients to create applications designed specifically to run on the provider’s hardware (platforms). The vendor provides the hosting environment and programming tools to permit customers to build solutions for the specific environment.

Software as a Service (SaaS)
Software is provided as a resource in the form of applications that run on the provider’s hardware. The consumer sees only the interface to the software, just like with a desktop application. The hardware, operating system, etc., are all hidden and controlled exclusively by the vendor. This is the oldest model currently included in definitions of the cloud, and for many decades it was known as an Application Service Provider (ASP).

The deployment models refer to the availability or accessibility of the resulting solutions and include:

Private
Access to resources is limited to the customer only.

Community
Access to resources is shared among one or more customers.

Public
Access to resources is available to the general public.

Hybrid
This is an infrastructure composed of two or more of the other models. Typically, this results in a division of private and public resources that can communicate.

A document with a complete discussion of the NIST’s view of cloud computing is located at http://csrc.nist.gov...loud-computing/.