Cloud computing is general purpose resources available on the web. They can be accessed using a browser such Internet explorer, Mozilla Firefox or Chrome. Cloud computing resources are available either free or on rental basis. Although most of us are already using one or more cloud computing resources, we are not consciously aware of them. For instance, many of us web based free email services such as G-mail or hotmail. Services such as above are made possible using cloud computing approach. The email service we use is called application service and our email transactions (such as sent email, inbox) are stored in remote servers called data centers.
Classifying Cloud Computing Resources
There are innumerable cloud computing products and services on the web, each with its distinct properties and functions. There are hundreds of distinct markets and different end uses, all kinds of ways to group customers, and many different channels to bring a product or service to its markets and customers.
Yet practically all cloud computing products and services can be classified under the following major categories
1. Application as service ( AaaS)
2. Platform as a Service (PaaS)
3. Infrastructure as a service (IaaS)
4. Software as a Service (SaaS)
1. Application as s service (AaaS): These are the first kind of cloud computing services that came into being. Under this, a service is made available to an end-user. The end-user is asked to create an account with the service provider and start using the application. One of first famous application was web-based email service by hotmail started in 1996. Scores of such services are available now on the web. For instance, Google Docs or MS’s are word processing applications available on the web for end users
2. Platform as a Service (PaaS): Cloud vendors are companies that offer cloud computing services and products. One of the services that they provide is called PaaS. Under this a computing platform such as operating system is provided to a customer or end user on a monthly rental basis. Some of the major cloud computing vendor are Amazon, Microsoft, Google etc
3. Infrastructure as a service: The cloud computing vendors offer infrastructure as a service. One may avail hardware services such as processors, memory, networks etc on agreed basis for specific duration and price.
4. Software as a service (SaaS): Software package such as CRM or CAD/CAM can be accessed under cloud computing scheme. Here a customer upon registration is allowed to use software accessible through net and use it for his or his business process. The related data and work may be stored on local machines or with the service providers. SaaS services may be available on rental basis or on per use basis.
