A better way to understand the cloud is to interpret everything as a service. A “service” corresponds to any facility provided by the cloud. There are three standard models to categorise different computing services delivered through cloud as shown in Figure. These are Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).
(A) Infrastructure as a Service (IaaS)
The IaaS providers can offer different kinds of computing infrastructure, such as servers, virtual machines (VM), storage and backup facility, network components, operating systems or any other hardware or software. Using IaaS from the cloud, a user can use the hardware infrastructure located at a remote location to configure, deploy and execute any software application on that cloud infrastructure. They can outsource the hardware and software on a demand basis and pay as per the usage, thereby they can save the cost of software, hardware and other infrastructures as well as the cost of setting up, maintenance and security.
(B) Platform as a Service (PaaS)
The facility provided by the cloud, where a user can install and execute an application without worrying about the underlying infrastructure and their setup. That is, PaaS provides a platform or environment to develop, test, and deliver software applications. Suppose we have developed a web application using MySQL and Python. To run this application online, we can avail a pre-configured Apache server from cloud having MySQL and Python pre-installed. Thus, we are not required to install MySQL and Python on the cloud, nor do we need to configure the web server (Apache, nginx). In PaaS, the user has complete control over the deployed application and its configuration. It provides a deployment environment for developers at a much reduced cost lessening the complexity of buying and managing the underlying hardware and software.
(C) Software as a Service (SaaS)
SaaS provides on-demand access to application software, usually requiring a licensing or subscription by the user. While using Google Doc, Microsoft Office 365, Drop Box, etc., to edit a document online, we use SaaS from cloud. A user is not concerned about installation or configuration of the software application as long as the required software is accessible. Like PaaS, a user is provided access to the required configuration settings of the application software, that they are using at present.
In all of the above standard service models, a user can use on-demand infrastructure or platform or software and is usually charged as per usage, thereby eliminating the need of a huge investment upfront for a new or evolving organisation. In order to utilise and harness the benefits of cloud computing, Government of India has embarked upon an ambitious initiative — “GI Cloud” which has been named as ‘MeghRaj’ (https:// cloud.gov.in).
