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Top1. Introduction
With the rapid growth in Information Technology (IT), cloud computing has emerged as the substitute for traditional computing technologies for providing services to clients at any time and any location on a pay-per-use basis (Garg & Shukla, 2019) . Cloud computing helps the user to pay for the resources that they have used instead of spending huge amount on operating, maintaining and integration (Priya & Jaisankar, 2019) (Abdel-Basset, Manogaran, Mohamed, & Rushdy, 2018). According to NIST, “Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction” (Mell & Grance, 2011). Cloud computing can be deployed into four forms: public, private, Hybrid and Community.
In the public cloud, the service providers present their services to the public through the internet and web applications (Abdel-Basset, Mohamed, & Chang, 2018).There is a security risk since applications from different users are mixed together on cloud servers but is cost-effective (Naz, Naaz, & Biswas, 2020). An example is Amazon Web Services (AWS) offering Elastic Compute Cloud (EC2) to anyone with a credit card. Typically, server rental prices are charged on a per-hour rental basis (Sehgal, Bhatt, & Acken, 2020).
Private Cloud is owned and managed by a single organization that only offers services to its users (and maybe its partners) over a private LAN on demand through a self-service portal (Surianarayanan & Chelliah, 2019). Information is stored in an organization’s privatized servers. It is mostly targeted towards keeping control over an organization’s characteristics and information along with keeping the necessary security (Gourisaria, Samanta, Saha, Patra, & Khilar, 2020). An example is an enterprise that offers Cloud-based services behind corporate fire-walls to its employees located at different sites. Internal departments contribute or pay to build such a Cloud, typically maintained by the corporate IT services (Sehgal et al., 2020).
A community cloud is a cloud service model that provides a cloud computing solution to a limited number of organizations (or a few communities) that have similar security, privacy, governance, and management policies (Surianarayanan & Chelliah, 2019). With the expenditure distributed over a less number of users than public cloud, community cloud provides a high level of security and privacy (Gourisaria et al., 2020). An example of community cloud is Google’s Gov. Cloud.
A hybrid cloud is a combination of public and private clouds bound together by either standardized or proprietary technology that enables data and application portability (Surianarayanan & Chelliah, 2019). Hybrid cloud supports applications to run simultaneously on two different cloud architectures, eliminating cloud bursting situations or failovers (Dhirani, Newe, & Nizamani, 2018).
The services of cloud computing are broadly classified into three types: Software as a Service (SaaS), Platform as a Service (PaaS) and Infrastructure as a Service (IaaS) (Siddiqui, Darbari, & Yagyasen, 2019).