Cloud computing is a combination of two words, “CLOUD” which is referred as a metaphor for “THE INTERNET”. “Cloud computing” implies the service based on internet computing, where different kinds of services like storage, servers and applications are sorted and delivered to the organizations computers and devices through the internet.

Cloud computing is a high demanded service and has achieved mass appeal in corporate data centers. In the service cloud manages the data center to work like Internet along with computing resources to be accessed and shared as virtual resources in a secure and ascendable manner. The accessibility of low cost computer devices, high-networking system, storage devices, service oriented architecture, autonomic and utility computing as well as hardware virtualization has contributed in the growth of CLOUD COMPUTING.

The cloud promises to lower down costs and helps the users to focus on their business and working instead of involving with obstruction or impediments of IT. The main technology that forwards cloud computing is “VIRTUALIZATION”. Virtualization software helps in separating a physical computing device into one or more “virtual” devices which can be easily used and managed for performing computing tasks. Cloud computing share its features with:

  1. Client-server model: Client server model refers widely to any organised application which differentiates between service providers (servers) and service requestor (clients).
  2. Computer bureau: It is a service bureau which has been providing computer services from 1960s to 1980s.
  3. Grid computing: Grid computing is a form of distributed and parallel computing where a super and virtual computer, composing a cluster of network, acting to perform very large tasks and functions. 
  4. Utility computing: The package of computing resources such as computation and storage and the services similar to traditional public utility. For example: Electricity.
  5. Fog computing: It is a distributed computing program which ensures data, computing, storage and application services closely related to near-user edge devices such as network routers. 
  6. Cloud sandbox: It is an isolated computer environment where a program, code or file can run without disturbing the application in which it use to run.
  7. Peer to peer: Peer to peer means in a connected chain. It does not need a central node for coordination along this the participants are both consumers and suppliers of the resources.

The three important deployment models of cloud computing are PRIVATE, PUBLIC AND HYBRID CLOUD. The National Institute of Standards and Technology’s definition identifies “five main essentials” of cloud computing. 

  • On demand self service
  • Broad network access
  • Rapid elasticity
  • Resource pooling
  • Measured services



Cloud computing providers provides their services with the different service models, among which the three standard models are IaaS ( Infrastructure as a Service), PaaS (Platform as a Service), SaaS (Software as a Service). All these three models provides the increasing abstraction and thus they are portrayed as layers in the stack. 


IaaS refers to the onlineservices which are meant to provide high level APIs used to dereferences various low level network of underlying network infrastructure. IaaS cloud providers provides the resources on demand from their big collection of equipments installed in data centers. 


NIST defines PaaS as:  

 “The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages, libraries, services, and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment.” PaaS vendors offers a development environment to the application developers.


NIST defines SaaS as:

“The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.”

Other service models of Cloud computing are:


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