Cloud Computing

Cloud Computing
A Cloud, of course, is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the earth. It is also a visible mass attracted by gravity. Lately, Cloud Computing has been exerting a strong gravitational pull of its own-one that has been attracting a mass of money.
So, a cloud computing is a dynamic delivery of information technology resources and capabilities as a service over the internet. Cloud computing is a style of computing in which dynamically scalable and often virtualized resources are provided as a service over the internet.
Cloud computing is a natural development to meet needs that have been evident for more than forty years. Virtualization is a key technology that enables cloud computing.
Cloud computing generally incorporated as,
-          Infrastructure as a Service (IaaS)
-          Platform as a Service (PaaS)
-          Software as a Service (SaaS)
The most frequently cited benefits of cloud computing are:
-          It is agile, with ease and speed of development.
-          Its cost is use-based, and will likely be reduced.
-          In-house IT costs are reduced.
-          Capital investment is reduced.
-          The latest technology is always delivered.
-          The use of standard technology is encouraged and facilitated.
The National Institute for Standards and Technology (NIST) defines the cloud computing as,
‘Cloud Computing is a model for enabling 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. The cloud model of computing promotes the availability. ‘
Characteristics of Cloud Computing:
-          On-demand Self Service
-          Broad network access
-          Resource pooling
-          Rapid elasticity
-          Measured Services
Cloud Service Models:
There are three models of cloud computing. They are:
a)    Software as a Service (SaaS):
The capability provided to the consumers in this highest level is to use of the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g. web-based e-mail). 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 execution of limited user-specific applications configuration settings. 
b)    Platform as a Service (PaaS):
The capability provided to the consumer in this intermediate level is to deploy onto the cloud infrastructure consumer-created or acquired applications developed using programming languages 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 application hosting environment configurations.
c)    Infrastructure as a Service (Iaas):
The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating system and applications. The consumer does not manage or control the underlying cloud information but has control over operating system. Storage, deployed applications, and possibly limited control of select networking components (e.g. host, firewalls).
Deployment Models:
There are four different deployment models of cloud computing. They are :
a)    Private Cloud: The cloud infrastructure is operating solely for an organization. It may be managed by the organization or a third party and may exist on premise or off primise.
b)      Community Cloud: The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g. mission, security requirements, policy and compliance consideration). It may be managed by the organizations or a third party and may exist on premise or off premise.
c)      Public Cloud: The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.
d)    Hybrid Cloud: The cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g. cloud bursting for load-balancing between clouds).