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 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 network-

based services, which appear to be provided by real

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

other businesses or individuals.  Cloud providers

are sometimes referred to as cloud service

providers or CSPs.

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.

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.

Public Cloud Providers

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

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.

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, code-named 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

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.

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, enterprise-class 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 data-intensive, 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 cloud-based 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 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. 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.

J. VM Ware

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 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

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

provider’s other customers. The provider can, and

does, logically and physically segment customer

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-

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

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

customer.

In a PaaS architecture, the provider will often

claim responsibility for certifying the solution

stack, virtual machine, hypervisor, compute &

storage, network and physical facility tiers. The

generated data, application configurations and

methods for presenting the data are the sole

responsibility of the PaaS customer.

Infrastructure-as-a-service (IaaS) provider

environments give you the closest architecture to

that of an on-premises 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.

IV. Market Trends from 2003 to 2013

Fig 3: Tends in market

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

Gartner. In it is a section that talks about how new

security management thinking must take place

when an organization looks at public cloud

services.

It is important that organizations understand the

risks in adopting the use of public cloud services.

Legislation, regulatory requirements, and

organization policies and procedures will not

change as quickly as the cloud evolves. Embarking

on a cloud strategy means an organization is

subject to threats above and beyond what it is

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

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

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 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 5: Examples of vendors providing public cloud services

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

with low speed connection Can be slow Data stored might not be secure Stored data can be lost.

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.

Fig 8: Economic efficiency v/s scale graph

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

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.

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:

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[4] http:// www.ibm.com /cloud-computing/us/en /

[5] http:// www.zdnet.com

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[7]http://searchcloudprovider.techtarget.com/def inition/cloud-provider

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