International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
A REVIEW ON CLOUD COMPUTING
Battina Dinesh#1, B.Veera Mallu*2
#
Final Year B.Tech, Dept. of CSE, K L University, Vaddeswaram, AP, India
*Associate Professor, Dept. of CSE, K L University, Vaddeswaram, AP, India
Abstract — Cloud computing describes computation, software,
data access, and storage services that do not require end-user
knowledge of the physical location and configuration of the
system that delivers the services.Cloud computing is a natural
evolution of the widespread adoption of virtualization,
service, autonomic and utility computing. Details are abstracted
from end-users, who no longer have need for expertise in, or
control over, the technology infrastructure "in the cloud" that
supports them.Cloud computing describes a new supplement,
consumption, and delivery model for IT services based on
Internet protocols, and it typically involves provisioning of
dynamically scalable and often virtualized resources.It is a
byproduct and consequence of the ease-of-access to
remote computing sites provided by the Internet. This frequently
takes the form of web-based tools or applications that users can
access and use through a web browser as if it were a program
installed locally on their own computer
Keywords— Client, Application, Platform, Infrastructure,Server.
I. INTRODUCTION
Cloud computing is a pay-per-use model for
enabling available, convenient, on-demand network access to
a shared pool of configurable computing resources (e.g.,
networks, servers, storage, applications, services) that can be
rapidly provisioned and released with minimal management
effort or service provider interaction. This cloud model
promotes availability and is comprised of five key
characteristics, three delivery models, and four deployment
models.
The National Institute of Standards and
Technology (NIST) provide a somewhat more objective and
specific definition:
 "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 term "cloud" is used as a metaphor for the Internet, based
on the cloud drawing used in the past to represent the
telephone network, and later to depict the Internet in computer
network diagrams as an abstraction of the underlying
infrastructure it represents. Most cloud computing
Infrastructures consist of services delivered through common
centers and built on servers. Clouds often appear as single
points of access for consumers' computing needs.
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Commercial offerings are generally expected to meet quality
of service (QoS) requirements of customers, and typically
include service level agreements (SLAs)
II. COMPARISONS
Cloud computing derives characteristics from, but should not
be confused with:
1. Autonomic computing — computer systems capable
of self-management
2. Client–server model – client–server computing refers
broadly
to
any distributed
application that
distinguishes between service providers (servers)
and service requesters (clients).
3. Grid computing —
"a
form of distributed
computing and parallel computing, whereby a 'super
and virtual computer' is composed of a cluster of
networked, loosely coupled computers acting in
concert to perform very large tasks"
4. Mainframe computer — powerful computers used
mainly by large organizations for critical
applications, typically bulk data-processing such
as census,
industry
and
consumer
statistics, enterprise
resource
planning,
and
financial transaction processing
5. Utility computing — the "packaging of computing
resources, such as computation and storage, as a
metered service similar to a traditional public utility,
such as electricity"
6. Peer-to-peer – distributed architecture without the
need for central coordination, with participants being
at the same time both suppliers and consumers of
resources (in contrast to the traditional client–server
model)
7. Service-oriented computing – Cloud computing
provides services related to computing while, in a
reciprocal manner, service-oriented computing
consists of the computing techniques that operate on
software-as-a-service.
III. CHARACTERISTICS
The key characteristic of cloud computing is that
the computing is "in the cloud" i.e. the processing (and the
related data) is not in a specified, known or static place(s).
This is in contrast to a model in which the processing takes
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place in one or more specific servers that are known. All the
other concepts mentioned are supplementary or
complementary to this concept.
A.KEY CHARACTERSTICS:
On-demand self-service : A consumer can unilaterally
provision computing capabilities, such as server time and
network storage, as needed without requiring human
interaction with each service’s provider.
Ubiquitous network access: Capabilities are available over the
network and accessed through standard mechanisms that
promote use by heterogeneous thin or thick client platforms
(e.g., mobile phones, laptops, and PDAs).
Location independent resource pooling : The provider’s
computing resources are pooled to serve all consumers using a
multi-tenant model, with different physical and virtual
resources dynamically assigned and reassigned according to
consumer demand. The customer generally has no control or
knowledge over the exact location of the provided resources.
Examples of resources include storage, processing, memory,
network bandwidth, and virtual machines.
Rapid elasticity: Capabilities can be rapidly and elastically
provisioned to quickly scale up and rapidly released to quickly
scale down. To the consumer, the capabilities available for
rent often appear to be infinite and can be purchased in any
quantity at any time.
Pay per use: Capabilities are charged using a metered, fee-forservice, or advertising based billing model to promote
optimization of resource use. Examples are measuring the
storage, bandwidth, and computing resources consumed and
charging for the number of active user accounts per month.
Clouds within an organization accrue cost between business
units and may or may not use actual currency.
Agility improves with users' ability to rapidly and
inexpensively re-provision technological infrastructure
resources.
Application Programming Interface (API) accessibility to
software that enables machines to interact with cloud software
in the same way the user interface facilitates interaction
between humans and computers. Cloud Computing systems
typically use REST-based APIs.
Cost is claimed to be greatly reduced and in a public cloud
delivery model capital expenditure is converted to operational
expenditure. This ostensibly lowers barriers to entry, as
infrastructure is typically provided by a third-party and does
not need to be purchased for one-time or infrequent intensive
computing tasks. Pricing on a utility computing basis is fine-
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grained with usage-based options and fewer IT skills are
required for implementation (in-house).
Device and location independence enable users to access
systems using a web browser regardless of their location or
what device they are using (e.g., PC, mobile). As
infrastructure is off-site (typically provided by a third-party)
and accessed via the Internet, users can connect from
anywhere.
Multi-tenancy enables sharing of resources and costs across a
large pool of users thus allowing for Centralization of
infrastructure in locations with lower costs (such as real estate,
electricity, etc.).
Peak-load capacity increases (users need not engineer for
highest possible load-levels).
Reliability is improved if multiple redundant sites are used,
which makes well designed cloud computing suitable
for business continuity and disaster recovery. Nonetheless,
many major cloud computing services have suffered outages,
and IT and business managers can at times do little when they
are affected.
Scalability via
dynamic
("on-demand") provisioning of
resources on a fine-grained, self-service basis near real-time,
without
users
having
to
engineer
for
peak
loads. Performance is monitored, and consistent and loosely
coupled architectures are constructed using web services as
the system interface.
Security could improve due to centralization of data, increased
security-focused resources, etc., but concerns can persist about
loss of control over certain sensitive data, and the lack of
security for stored kernels. Security is often as good as or
better than under traditional systems, in part because providers
are able to devote resources to solving security issues that
many customers cannot afford. Providers typically log
accesses, but accessing the audit logs themselves can be
difficult or impossible. Furthermore, the complexity of
security is greatly increased when data is distributed over a
wider area and / or number of devices.
Maintenance of cloud computing applications is easier, since
they don't have to be installed on each user's computer. They
are easier to support and to improve since the changes reach
the clients instantly.
Metering means that cloud computing resources usage should
be measurable and should be metered per client and
application on a daily, weekly, monthly, and yearly basis.
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A. Client:
IV. ARCHITECTURE
A cloud client consists of computer hardware and/or computer
software that relies on cloud computing for application
delivery, or that is specifically designed for delivery of cloud
services and that, in either case, is essentially useless without
it. Examples include some computers, phones and other
devices, operating systems and browsers.
B. Application:
Cloud application services or "Software as a
Service (SaaS)" deliver software as a service over the Internet,
eliminating the need to install and run the application on the
customer's own computers and simplifying maintenance and
support. People tend to use the terms ‘SaaS’ and ‘cloud’
interchangeably, when in fact they are two different things.
C. Platform:
1)
Cloud architecture, the systems architecture of
the software systems involved in the delivery of cloud
computing,
typically
involves
multiple cloud
components communicating with each other over application
programming interfaces, usually web services and 3-tier
architecture. This resembles the UNIX philosophy of having
multiple programs each doing one thing well and working
together over universal interfaces. Complexity is controlled
and the resulting systems are more manageable than
their monolithic counterparts.
The two most significant components of cloud
computing architecture are known as the front end and the
back end. The front end is the part seen by the client, i.e. the
computer user.
V. LAYERS
The Internet functions through a series of network
protocols that form a stack of layers, as shown in the figure
(or as described in more detail in the OSI model). Once an
Internet Protocol connection is established among several
computers, it is possible to share services within any one of
the following layers.
Cloud platform services or "Platform as a
Service (PaaS)" deliver a computing platform and/or solution
stack as a service, often consuming cloud infrastructure and
sustaining cloud applications. It facilitates deployment of
applications without the cost and complexity of buying and
managing the underlying hardware and software layers
D. Infrastructure:
Cloud infrastructure services, also known as
"Infrastructure
as
a
Service
(IaaS)",
delivers computer infrastructure typically
a platform
virtualization environment - as a service. Rather than
purchasing servers, software, data-center space or network
equipment, clients instead buy those resources as a fully
outsourced service. Suppliers typically bill such services on
a utility computing basis and amount of resources consumed
(and therefore the cost) will typically reflect the level of
activity. IaaS evolved from virtual private server offerings.
E. Server:
The server’s layer
consists
of computer
hardware and/or computer
software products
that
are
specifically designed for the delivery of cloud services,
including multi-core processors, cloud-specific operating
systems and combined offerings.
VI. DELIVERY MODELS:
Cloud Software as a Service (SaaS): The capability provided
to the consumer is to use the provider’s applications running
on a cloud infrastructure and accessible from various client
devices through a thin client interface such as a Web browser
(e.g., web-based email). The consumer does not manage or
control the underlying cloud infrastructure, network, servers,
operating systems, storage, or even individual application
capabilities, with the possible exception of limited userspecific application configuration settings.
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Cloud Platform as a Service (PaaS): The capability provided
to the consumer is to deploy onto the cloud infrastructure
consumer-created applications using programming languages
and tools supported by the provider (e.g., java, python, .Net).
The consumer does not manage or control the underlying
cloud infrastructure, network, servers, operating systems, or
storage, but the consumer has control over the deployed
applications and possibly application hosting environment
configurations.
Cloud Infrastructure as a Service (IaaS): The capability
provided to the consumer is to rent processing, storage,
networks, and other fundamental computing resources where
the consumer is able to deploy and run arbitrary software,
which can include operating systems and applications. The
consumer does not manage or control the underlying cloud
infrastructure but has control over operating systems, storage,
deployed applications, and possibly select networking
components (e.g., firewalls, load balancers).
VII. DEPLOYMENT MODELS
community that has shared concerns (e.g., mission, security
requirements, policy, and compliance considerations).
C. Hybrid cloud:
There is some confusion over the term "hybrid"
when applied to the cloud - a standard definition of the term
"Hybrid Cloud" has not yet emerged. The term "hybrid cloud"
has been used to mean either two separate clouds joined
together (public, private, internal or external), or a
combination of virtualized cloud server instances used
together with real physical hardware. The most correct
definition of the term "hybrid cloud" is probably the use of
physical hardware and virtualized cloud server instances
together to provide a single common service. Two clouds that
have been joined together are more correctly called a
"combined cloud".
D. Private cloud:
Douglas Parkhill first described the concept of a
"private computer utility" in his 1966 book The Challenge of
the Computer Utility. The idea was based upon direct
comparison with other industries (e.g. the electricity industry)
and the extensive use of hybrid supply models to balance and
mitigate risks.
Private cloud and internal cloud have been
described as neologisms, however the concepts themselves
pre-date the term cloud by 40 years. Even within modern
utility industries, hybrid models still exist despite the
formation of reasonably well-functioning markets and the
ability to combine multiple providers. Some vendors have
used the terms to describe offerings that emulate cloud
computing on private networks. These (typically virtualization
automation) products offer the ability to host applications or
virtual machines in a company's own set of hosts.
A. Public Cloud:
Public cloud or external cloud describes cloud
computing in the traditional mainstream sense, whereby
resources are dynamically provisioned on a fine-grained, selfservice basis over the Internet, via web applications/web
services, from an off-site third-party provider who bills on a
fine-grained utility computing basis. The cloud infrastructure
is owned by an organization selling cloud services to the
general public or to a large industry group.
B. Community cloud:
A community cloud may be established where
several organizations have similar requirements and seek to
share infrastructure so as to realize some of the benefits of
cloud computing. With the costs spread over fewer users than
a public cloud (but more than a single tenant) this option is
more expensive but may offer a higher level of privacy,
security and/or policy compliance. Examples of community
cloud include Google's "Gov Cloud". The cloud infrastructure
is Shared by several organizations and supports a specific
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VIII. CLASSIFICATION OF CLOUD ON THE BASIS OF
SERVICE PROVIDED:
Infrastructure as a service(IAAS): Hardware related services
are provided using the principles of Cloud Computing. These
include disk storage and virtual servers. Amazon EC2,
Amazon S3, Rackspace Cloud Servers are some of the leading
vendors.
Platform as a service(PAAS): Development platforms are
provided on the cloud. The platforms may not be compatible
with each other.‘Platform as a service’ (PaaS) the delivery of
a computing platform and solution stack as a service.PaaS
offerings facilitate deployment of applications without the
cost and complexity of buying and managing the underlying
hardware and software and provisioning hosting capabilities,
providing all of the facilities required to support the complete
life cycle of building and delivering web applications and
services entirely available from the Internet.PaaS offerings
may include facilities for application design, application
development, testing, deployment and hosting as well as
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application services such as team collaboration, web service
integration and marshalling, database integration, security,
scalability, storage, persistence, state management, application
versioning, application instrumentation and developer
community facilitation. These services may be provisioned as
an integrated solution over the web.Google App Engine,
Microsoft Azure and Saleforce’s force.com are the leaders in
this category.
Software as a service (SAAS): This is the most common form
of cloud computing which we see in action. It is a complete
software offering on the cloud. They are accessed by the
customers on pay per use basis. Saleforce.com’s CRM,
Google apps etc are the prime example of such a service.
Salesforce.com’s CRM, Gmail and Hotmail are prime
examples of SAAS.
services are less secure. What the company is failing to
recognize is that they are probably already using such services
without consideration. Services like Blackberry, Message labs
and other such services involve messages being sent to a third
party, scanned then forwarded back into the organizations
localized mail stream. This would undoubtedly change most
people’s perspective as a well run cloud solution far
outweighs the perception of insecurity and loss of control. In
fact, in many cases the solution is to build better hardware,
firmer controls and more efficient infrastructure at a lower
cost.
XI.PROS AND CONS OF CLOUD COMPUTING

Cloud computing can enable the constant flow of
information between the outsourced service and the
outsourcing service. Other remote systems would
struggle with such a task because they are based on
database communications that are largely outdated. The
ease with which the information can be accessed gives
confidence to the employees of the outsourcing
organization that they can continue with their normal
work despite the introduction of cloud computing.

The pay as you go model of cloud computing adds
considerable savings potential to the company’s portfolio.
One of the issues that concerns managers is the impact of
idle time on the overall cost of information technology.
If you are using an external entity for the management of
the IT portfolio, then you can write an agreement that
will only charge you for when you use the IT facilities.
The main problems with cloud computing are related to
the loss of control to another party. This can lead to
supervision problems and conflict within the information
technology departments. You will have to set up new
systems for dealing with this conflict and you will have
IX. CLOUD STORAGE
Cloud storage is a model of networked computer
data storage where data is stored on multiple virtual servers,
generally hosted by third parties, rather than being hosted on
dedicated servers. Hosting companies operate large data
centers; and people who require their data to be hosted buy or
lease storage capacity from them and use it for their storage
needs.
The data
center operators,
in
the
background, virtualize.The resources according to the
requirements of the customer and expose them as virtual
servers, which the customers can themselves manage.
Physically, the resource may span across multiple servers.
X. SECURITY
The relative security of cloud computing services
is a contentious issue which may be delaying its
adoption. Issues barring the adoption of cloud computing are
due in large part to the private and public sectors unease
surrounding the external management of security based
services. It is the very nature of cloud computing based
services, private or public, that promote external management
of provided services. This delivers great incentive amongst
cloud computing service providers in producing a priority in
building and maintaining strong management of secure
services.
Organizations have been formed in order to
provide standards for a better future in cloud computing
services. One organization in particular, the Cloud Security
Alliance is a non-profit organization formed to promote the
use of best practices for providing security assurance within
cloud computing.
Security is always a concern, especially when
running environments like windows that are so familiar the
world over. Microsoft has a reasonable patch management
solution but now in the cloud this effectively can be delivered
in minutes rather than days.In many cases, some organizations
have the view that cloud solutions outsourcing and managed
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to configure your communication systems on the basis
that there is another company involved in your business.
Sometimes cloud computing will have so many teething
problems that it might take years before you settle into
an agreement with your supplier whereby conflicts can
be resolved before they escalate.
XII.BENEFITS OF CLOUD COMPUTING
There are many benefits to a cloud solution, but these need to
be weighed and understood before opting for a solution that is
partially out of the IT departments control. Below we will
cover some of the benefits, components and countermeasures
that need to be understood before opting in.
Greener: Cloud solutions tend to be greener, as some of the
infrastructure is co hosted and shared, some of the
applications and solutions are fully virtualized and other
design changes make the whole offering more efficient and
thus greener. In the UK, if an enterprise hosts a typical
exchange server, the electrical costs usually add up to over
£500 per year. A collocated server with similar specification
and computing power would cost less than half this in the
cloud. Then there is the question of licensing. Typical vendor
licensing cost can vary based on size of enterprise. In most
cases, service providers have cumulative packages that make
the full cloud subscription cheaper for the consumer as the
service providers have better deals with vendors. In turn, the
cloud delivered solution is much cheaper from a hosting and
licensing perspective. The skills are also cumulative so the
customer benefits from enhanced expert skill.
solution. This would make the cost prohibitive and most
organizations would not consider this solution; however this is
exactly what happened in the beginning of the cell phone
service 15 years ago, and how the offering was funded. Today,
the cost of mobile telephony has dropped and become
affordable. Evidently, people now subscribe without a second
thought and this is a fully managed, wireless “cloud” type
service funded by subscription and the numbers.
XIII.CLOUD COMPUTING IN FUTURE
In the future, more cloud adoption is certain, this year alone
the move to the cloud by many business has been phenomenal,
so much so that some cloud business have grown by over
200%. Large vendors see this as the growing model for
software and services in the future so more focus by the
vendors is afforded. Do not be surprised if the cloud bursts
with offerings over the next 24 months.
XIV.REFERENCES
[1] T Velte, A Velte, R Elsenpeter - 2009 - dl.acm.org
[2] P Mell, T Grance - NIST special publication, 2011 - predeveloper.att.com
[3] L Youseff, M Butrico, D Da Silva - Grid Computing …,
2008 - ieeexplore.ieee.org
[4] R Buyya, CS Yeo, S Venugopal, J Broberg… - Future
Generation …, 2009 - Elsevier
[5] M Armbrust, A Fox, R Griffith, AD Joseph… Communications of the …, 2010 - dl.acm.org
Most managed services are looked after by dedicated teams
per solution. This means that the solution is built by
specialists that focus on the particular technology. The
outcome is that the offering is more streamlined and a service
runs within the best practice guidelines of the vendor and
industry. This would be markedly different compared to
“home” or internally built enterprise solutions that cannot
emulate the level of a cloud service.
Centralized: The centralized yet potentially decentralized
management solution. This fully scalable and flexible cloud
solution offers something that is difficult to achieve for most
large enterprises. Compared to locally hosted applications a
cloud solution would offer company flexibility and reach that
any global business would envy. This is very compelling, and
on many occasions, this feature can be the sole reason for an
organization to move into the cloud.
Affordable: One of the important considerations to a cloud
service is cost. Imagine having to pay for all the cell phone
towers used every time you wanted to buy a mobile
phone. This would mean that to use the infrastructure, an
individual or enterprise would have to pay for the towers, the
connectivity between them and all the other elements of the
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