A set of computers and computer network resources based on the standard cloud computing model, in which a service provider makes resources, such as applications and storage, available to the general public over the Internet . Public cloud services may be free or offered on a pay-per-usage model. Applications, storage, and other resources are made available to the general public by a service provider. There are service providers like Amazon, Microsoft or Google who own all infrastructure at their data center.

1. Public Cloud Providers
Abstract: Cloud computing is a phrase used to
describe a variety of computing concepts that involve
a large number of computers connected through a
real-time
communication network such
as
other businesses or individuals. Cloud providers
are sometimes referred to as cloud service
providers or CSPs.
the
Internet. In science, cloud computing is a synonym
for distributed computing over a network, and means
the ability to run a program or application on many
connected computers at the same time.
The phrase is often used in reference to networkbased services, which appear to be provided by real
There are a number of things to think about when
you evaluate cloud providers. The cost will usually
be based on a per-use utility model but there are a
number of variations to consider. The physical
location of the servers may also be a factor for
sensitive data.
server hardware, and are in fact served up by virtual
hardware, simulated by software running on one or
more real machines. Such virtual servers do not
physically exist and can therefore be moved around
and scaled up or down on the fly without affecting the
end user, somewhat like a cloud becoming larger or
smaller without being a physical object.
In common usage, the term "the cloud" is essentially
a metaphor for the Internet. Marketers have further
popularized the phrase "in the cloud" to refer to
software, platforms and infrastructure that are
sold "as a service", i.e. remotely through the Internet.
Typically, the seller has actual energy-consuming
servers which host products and services from a
remote location, so end-users don't have to; they can
simply log on to the network without installing
anything. The major models of cloud computing
service are known as software as a service, platform
as service, and infrastructure as a service. These
cloud services may be offered in a public, private or
hybrid
network. Google, Amazon, Salesforce,
and Microsoft Azure are some well-known cloud
vendors.
Keywords: Public cloud, PaaS, SaaS, IaaS, services,
computing resources, applications, service providers,
clouds, networking.
I.INTRODUCTION
A cloud provider is a company that offers some
component of cloud computing – typically
Infrastructure as a Service (IaaS), Software as a
Service (SaaS) or Platform as a Service (PaaS) – to
Reliability is crucial if your data must be
accessible. A typical cloud storage service-level
agreement (SLA), for example, specifies precise
levels of service – such as, for example, 99.9%
uptime – and the recourse or compensation that the
user is entitled to should the provider fail to
provide the service as described. However, it’s
important to understand the fine print in that
agreement because some providers discount
outages of less than ten minutes, which may be too
long for some businesses.
Security is another important consideration.
Organizations such as the Cloud Security Alliance
(CSA) offer certification to cloud providers that
meet their criteria. The CSA's Trusted Cloud
Initiative program was created to help cloud service
providers develop industry-recommended, secure
and interoperable identity, access and compliance
management configurations and practices.
Amazon was the first major cloud provider, with
the 2006 offering of Amazon Simple Storage
Service (Amazon S3). Other cloud providers
include Apple, Cisco, Citrix, IBM, Joyent, Google,
Microsoft,
Rackspace,
Salesforce.com and
Verizon/Terremark.
A public cloud is a set of computers and computer
network resources based on the standard cloud
computing model, in which a service provider
makes resources, such as applications and storage,
available to the general public over the Internet .
Public cloud services may be free or offered on a
pay-per-usage model.

2. Applications, storage, and other resources are made
available to the general public by a service
provider. There are service providers like Amazon,
Microsoft or Google who own all infrastructure at
their data centre, as well as Cloud Brokers who
aggregate infrastructure from multiple providers.
Public clouds are owned and operated by
companies that use them to offer rapid access to
affordable computing resources to other
organizations or individuals. With public cloud
services, users don’t need to purchase hardware,
software or supporting infrastructure, which is
owned and managed by providers.
Fig 1. Public cloud v/s Private cloud v/s Hybrid
cloud
B. Rackspace
Rackspace Inc. may be this year's sleeping
giant. Although it hasn't made any billion-dollar
acquisitions the way several competitors have in
2012, the co-creator of the Open Stack open source
cloud OS is positioned to remain a leader on the
cloud provider rolls. In fact, the OpenStack
community just shipped its fifth release, codenamed Essex, in early April. Rackspace, which
started out as a custom applications hosting
company in 1998, provides traditionally managed
hosting as well as public cloud Platform as a
Service (PaaS), and hybrid cloud services that
blend the two technologies. The company grossed
almost $1.3 billion in fiscal 2011, up from $629
million in 2009, pushing growth well into double
digits annually with about a fifth of that coming
from its cloud businesses last year. The company
began the year with 4,040 employees -- who are
referred to as "rackers" -- more than 170,000
customers and nearly 80,000 servers in more than
233,000 square feet of data center space
worldwide.
C. CenturyLink/Savvis
II. TOP 10 PUBLIC CLOUD PROVIDERS OF
2012
A. Amazon Web Services
For the third year in a row, Amazon Web
Services (AWS) tops list, and not just by dint of
remaining the dominant player in public cloud
computing worldwide. Over the past year, AWS
has been on a roll shipping a rich variety of new
services targeting enterprise IT, a market that has
proved hard to penetrate for public cloud providers
but promises great returns for those that do.
Additionally, in a strategy to drive the market to
follow its moves, AWS has cut prices 19 times in
just the past six years. Although Amazon.com
doesn't fully break out its cloud services revenues,
AWS would appear to be a $6 billion company
based on its performance in 2011. That's in
comparison to Amazon.com's overall revenues of
$48 billion for the year -- not bad for a business
reputedly created to sell the e-retailer's excess
compute capacity back in 2002.
One of three telcos to make year’s
list, CenturyLink demonstrated how serious it is
about becoming a top-tier cloud services player
when it snapped up Savvis Inc. in a deal valued at
just under $2.7 billion last year. At least on paper,
the merging of CenturyLink’s hosting, networking
and other infrastructure assets, married with
Savvis’ collection of cloud products, colocation
and managed hosting cloud services, figures to
make the company a formidable competitor going
forward. The two companies now have a network
of 48 international data centres with nearly 2
million square feet of floor space. Another asset
Savvis will appreciate is CenturyLink’s deep
pockets: CenturyLink completed its acquisition of
Qwest Communications last year, a deal worth
$10.6 billion. The combined company has revenues
of $18.7 billion with earnings of $8.1 billion. This
should be enough walking around money to
compete against big, cash-rich telcos such as
Verizon/Terremark and high-tech monsters like
EMC, HP, IBM and Microsoft.

3. D. Salesforce.com
Salesforce.com isn’t living on Cloud 9 yet, but
it appears ready to inhabit Cloud 2. The company
that successfully pioneered cloud-based, enterpriseclass CRM solutions, looks like it is poised to
charge into the next era of cloud computing. This
era, which its brash chairman and CEO, Marc
Benioff, refers to as Cloud 2, is one that is all about
social media, mobile computing and real
time. Salesforce believes its acquisition of
Heroku, with its popular Ruby Platform as a
Service, will help it establish a leadership position
there. The deal gives Salesforce access to all of
Heroku’s technology and intellectual assets, along
with its growing base of Ruby-based developers
that have delivered some 105,000 applications.
Another symbiotic element that should work in the
duo’s favor is that Heroku’s platform is designed
from the ground up to be multi-tenant, a hallmark
of Salesforce’s Force.com platform.
E. Verizon/Terremark
When Verizon/Terremark on Top 10 cloud
computing providers of 2011 list, its future as one
of the largest telco/cloud hybrids was still
uncertain. Would enterprise cloud consumers see
the value of the $1.4 billion deal? And would
Terremark be able to give enterprises the
customization they so desired? Well, a few things
have come to the fore since then: Terremark
certainly hasn’t lost its cloud presence and Verizon
definitely is not the only telco that sees the hot
cloud computing market as a lucrative investment.
Further proving its dedication to the enterprise
customer, Terremark launched its Enterprise Cloud
Private Edition -- a single-tenant environment
reportedly offering the level of security many large
enterprises and government agencies require. And
its OS- and network-agnostic strategy shows the
telco cloud understands the value of accessibility
and integration. Competition will be tight in 2012,
though, as other telco cloud service providers like
CenturyLink/Savvis, Level 3/Global Crossing and
even Tata Communications fight to be heard in a
market that’s cranking up the volume.
F. Joyent
Joyent Inc. has made some friends in high
places. In 2010, Dell chose Joyent to power its
cloud; the public cloud provider is also the cloud
engine behind several online gaming platforms as
well as LinkedIn, the popular professional social
network. This year, Joyent has been making
announcements left and right about new strategic
partnerships, focusing its efforts on dataintensive, high-performance applications, including
partnerships with Data Layer as a Service provider
Cloudant; Nodejitsu, which develops tools for
Node.js; and Venice, Calif.-based online media
startup-for-startups Amplify. With a major industry
focus in 2012 on big data and HPC, Joyent could
be on the right track. It will be interesting to see
how much clout the Infrastructure as a Service
provider has, especially as it continues to licenses
its cloud software to telcos that are just beginning
to launch their own cloud platforms.
G. Citrix
If market researcher IDC’s prediction that the
cloud infrastructure market will grow to $11 billion
by the end of next year is correct, then the folks
running Citrix are going to look pretty smart. Citrix
Systems Inc. has bought a basket of cloud
computing infrastructure and services companies
recently,
most
notably
Cloud.com.
Cloud.com’s Cloud Stack, an open source
Infrastructure as a Service (IaaS) platform, has
proved popular among cloud providers preferring
to deploy and manage open cloud services. What
should also distinguish Citrix is that Cloud.com’s
product isn’t built as a traditional server
virtualization
platform
with cloud
management layered on top. Rather, it enlists a
hypervisor-agnostic model better suited for
building larger public clouds. Cloud.com, along
with the purchase of ShareFile, a provider of cloudbased data storage, should complement Citrix’s
portfolio of virtualization and collaboration
products including XenServer, XenDesktop,
CloudGateway and GoToMeeting.
H. Bluelock
Bluelock has steadily gained visibility the last
several years by aligning itself closely
withVMware’s
vCloud
Datacenter and
by
delivering cloud services with a solid reputation for
reliability. The company, which connects users’
VMware data centers with its public cloud, has

4. made a comfortable living focusing largely on
small and midsize companies. It offers both cloud
hosting coupled with managed IT services,
something high on the want list of many IT shops.
The vendor so far has done a good job bolstering
the confidence of smaller companies to move their
mission-critical applications in the cloud and hopes
to convince more midsize companies to do the
same. Its 2012 roadmap calls for the company to
focus more on bigger picture issues such as
multiple virtual data center integration, Data
Recovery as a Service and the Global Cloud, a
place that’s sure to see a lot of action.
I.
Service(PaaS) aimed at helping build, test and
deploy clouds, is slowly gaining ground. VMware
is trying to position itself as the go-to guy, the
middleman and an enabler to help enterprises get to
private and public clouds. Whether businesses buy
into VMware’s channel approach -- and whether
these “clouds” turn out to be anything more than
virtual data centres -- remains to be seen. But one
thing’s for sure, VMware figures to be a force in
2012.
III. Cloud Providers Responsibility
Segmentation
Microsoft
Microsoft retained a spot on the list again as
much for its sheer tenacity and the promise of more
to come as the size of its check book. The company
has been very visible regarding its "all in"
commitment to the cloud, despite some missteps -notably the major management service outage that
hit a large cross section of its U.S. and European
Windows Azure users in February, a.k.a. the "leap
year" outage. Microsoft declines to say how it's
doing with Azure, although it's a safe bet the public
cloud business is still losing money. But like
Windows Phone and, before it, Xbox, Microsoft
shows no sign of giving up and continues to roll out
new data centers, including one planned for
Cheyenne, Wyo. Counting its hosted private cloud
productivity suite, Office 365, Microsoft claims
100,000 businesses are using its various online
services. The company delivered System Centre
2012 last week and is gearing up to deliver
Windows Server 8 later this year, which will
underlie its private cloud offerings.
Fig 2: Cloud Providers Responsibility
Segmentation
The division of PCI (Payment Card Industry)
responsibility
differs
among
infrastructure
providers and their respective service models. In a
traditional outsourced data centre, the physical
servers are typically your responsibility, but the
connective tissue (i.e., the network connectivity) is
often shared between your organization and the
J.
VM Ware
provider’s other customers. The provider can, and
does, logically and physically segment customer
It might seem strange to find VMware listed
on a cloud provider list. But when you dig into just
how involved the virtualization giant is -- and will
be -- on the cloud front in the next year or so, you
might stop questioning what we’re smoking. The
company’s vCloud Director 1.5, an automation
engine and management arm for private clouds, has
piqued the interest of enterprise IT and a few cloud
vendors and service providers including iland and,
most recently, Bluelock. And Cloud Foundry, the
now year-old open source Platform as a
servers using routers, switches, firewalls and other
common infrastructure equipment. In the case of a
shared server environment (i.e., virtual hosting), the
provider often employs logical segmentation
techniques and tools to segregate customer servers
from one another. Compliance with PCI-DSS
(Payment Card Industry Data Security Standard) is
usually easy to attain in data centre environments
as the model changes little from that of an on-

5. premises customer data centre. As long as the
customer can receive assurances from the provider
as to its implemented administrative controls,
customers can often work with their Qualified
Security
Assessors
(QSAs)
to
address
any
technological control shortcomings.
Where the demarcation line resides quickly
becomes blurry in cloud architectures. Most
software-as-a-service (SaaS) providers take the
Fig 3: Tends in market
brunt of the responsibility from the hardware layer
all the way up to presentation layer. In an SaaS
environment, customers must rely on the compliant
state of their provider and have little to no control
over how that state is achieved and monitored.
Platform-as-a-service (PaaS) providers, on the
other hand, tend to leave the compliance of the
application and presentation layer up to the
V. Organisational Control And Public Cloud
Services
One of the things is a terrific article titled, “Cloud
Computing Security in the Enterprise” by Dan
Blum, a former VP Distinguished Analyst at
customer.
Gartner. In it is a section that talks about how new
In a PaaS architecture, the provider will often
security management thinking must take place
claim responsibility for certifying the solution
when an organization looks at public cloud
stack, virtual machine, hypervisor, compute &
services.
storage, network and physical facility tiers. The
generated data, application configurations and
It is important that organizations understand the
methods for presenting the data are the sole
risks in adopting the use of public cloud services.
responsibility of the PaaS customer.
Legislation,
regulatory
requirements,
and
organization policies and procedures will not
Infrastructure-as-a-service
provider
change as quickly as the cloud evolves. Embarking
environments give you the closest architecture to
on a cloud strategy means an organization is
that
subject to threats above and beyond what it is
of
an
on-premises
(IaaS)
virtualized
server
infrastructure. Customers are responsible for
everything from the virtualized machine up to the
presentation
layer,
whereas
the
provider
is
responsible for the hypervisor to facility tiers. The
IaaS model forces customers and providers to work
closely to provide mutual adherence to the tenets of
the PCI DSS.
already
exposed
to.
Organizations
need
to
understand how risks transfer to the cloud when
investigating cloud service arrangements.
The more an organization leverages public cloud
services, the
more control shifts from the
organization, to the cloud service provider. For
example, a solution architecture that is completely
IV. Market Trends from 2003 to 2013
deployed on premise means the organization has,
for the most part, complete control of the
deployment. At the other extreme is an solution
that is entirely hosted by an external service

6. provider, whereby the control of the deployment is
mostly, of not entirely, controlled by the service
provider. The following diagram illustrates the
comparative control models that is typical of a
organizations cloud environment, moving from a
on premise scenario, to a public cloud services
scenario.
Fig 5: Examples of vendors providing public
cloud services
Fig 4: Organisational Control And Public Cloud
Services
VI. Examples of vendors providing public cloud
services
Some (non-exhaustive) examples of vendors
providing public cloud services can be found in the
table below
Fig 6: Examples of Company, category and their
offering of services.
VII. Pros and Cons of Public Cloud Computing
Cloud Computing Advantages Extremely cost
efficient Device and location independence
Scalability Unlimited storage capacity Flexibility
Reduced software maintenance Increased data
reliability.
Cloud Computing Disadvantages Requires a
constant internet connection Doesn’t work well

7. with low speed connection Can be slow Data stored
might not be secure Stored data can be lost.
CONCLUSION:
Cloud hosting services provide hosting for
websites on virtual servers which pull their
computing resource from extensive underlying
networks of physical web servers. It follows the
utility model of computing in that it is available as
a service rather than a product and is therefore
comparable with traditional utilities such as
electricity and gas. Broadly speaking the client can
tap into their service as much as they need,
depending on the demands of their website, and
they will only pay for what they use.
Fig 7: Pros and Cons of Public Cloud
Computing
VIII. ANALYSIS ON VARIOUS CLOUD
PROVIDERS.
The picture shows the Economic efficiency v/s
scale graph by various cloud providers.
It exists as an alternative to hosting websites on
single servers (either dedicated or shared servers)
and can be considered as an extension of the
concept of clustered hosting where websites are
hosted on multiple servers. With cloud hosting
however, the network of servers that are used is
vast and often pulled from different data centres in
different locations.
Acknowledgement:
I will like to thank our Prof. for giving the chance
to explore oneself.
References:
Fig 8: Economic efficiency v/s scale graph
[1] http://www.paulspatterson.com
[2] http://searchcloudcomputing.com
IX. Risk in Public Cloud Computing
Regulatory compliance : when outsourcing to a
provider , customer are responsible for the security
& integrity of their own data, even when it is held
by third party Data
segmentation/user access : finding ways to make
sure employees receive adequate access
Recovery : Data segmentation makes back-ups
more difficult Logging & Investigative
Support : Harder to know who altered the data and
where they came from
[3] http://www.datacenterjournal.com
[4] http://www.ibm.com/cloud-computing/us/en/
[5] http://www.zdnet.com
[6]http://www.ijser.org/paper/Cloud-Storage-Gate
way-for-Industry-Data-Base.html?gclid=
CICOy9ie6bwCFfFV4godzUYA2Q
[7]http://searchcloudprovider.techtarget.com/def
inition/cloud-provider
[8] http://www.info.com/public%20cloud%20prov
iders?cb=4&cmp=2848
[9] http://www.interoute.com/what-cloud-hosting