cloud computing is internet

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Cloud computing is Internet-based computing, whereby shared resources, software and

information are provided to computers and other devices on-demand, like a public utility.

It is aparadigm shiftfollowing the shift from mainframeto client-serverthat preceded itin the early '80s. Details are abstracted from the users who no longer have need of,

expertise in, or control over the technology infrastructure "in the cloud" that supportsthem.[1] Cloud computing describes a new supplement, consumption and delivery model

for IT services based on the Internet, and it typically involves the provision ofdynamically scalable and often virtualizedresources as a service over the Internet.[2][3] It

is a byproduct and consequence of the ease-of-access to remote computing sites provided

by the Internet.[4]

The term cloudis used as ametaphorfor the Internet, based on the cloud drawing used inthe past to represent the telephone network,[5] and later to depict the Internet incomputer

network diagramsas anabstractionof the underlying infrastructure it represents.[6]

Typical cloud computing providers deliver commonbusiness applications online which

are accessed from another web service or software like aweb browser, while thesoftwareanddata are stored onservers.

A technical definition is "a computing capability that provides an abstraction between the

computing resource and its underlying technical architecture (e.g., servers, storage,networks), enabling convenient, on-demand network access to a shared pool of

configurable computing resources that can be rapidly provisioned and released with

minimal management effort or service provider interaction."[7] This definition states thatclouds have five essential characteristics: on-demand self-service, broad network access,

resource pooling, rapid elasticity, and measured service.[7]

Cloud computing is Internet-based computing, whereby shared resources, software andinformation are provided to computers and other devices on-demand, like a public utility.

It is aparadigm shiftfollowing the shift from mainframeto client-serverthat preceded it

in the early '80s. Details are abstracted from the users who no longer have need of,

expertise in, or control over the technology infrastructure "in the cloud" that supports

them.[1] Cloud computing describes a new supplement, consumption and delivery modelfor IT services based on the Internet, and it typically involves the provision of

dynamically scalable and often virtualizedresources as a service over the Internet.[2][3] It

is a byproduct and consequence of the ease-of-access to remote computing sites providedby the Internet.[4]

The term cloudis used as ametaphorfor the Internet, based on the cloud drawing used in

the past to represent the telephone network,[5] and later to depict the Internet incomputer

network diagramsas anabstractionof the underlying infrastructure it represents.[6]

Typical cloud computing providers deliver commonbusiness applications online which

are accessed from another web service or software like aweb browser, while thesoftware

anddata are stored onservers.
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A technical definition is "a computing capability that provides an abstraction between the

computing resource and its underlying technical architecture (e.g., servers, storage,

networks), enabling convenient, on-demand network access to a shared pool ofconfigurable computing resources that can be rapidly provisioned and released with

minimal management effort or service provider interaction."[7] This definition states that

clouds have five essential characteristics: on-demand self-service, broad network access,resource pooling, rapid elasticity, and measured service.[7]

Comparisons

Cloud computing derives characteristics from, but should not be confused with:

1. Autonomic computing "computer systems capable ofself-management".[9]

2. Client-server Client-server computing refers broadly to any distributed

applicationthat distinguishes between service providers (servers) and servicerequesters (clients).[10]

3. Grid computing "a form ofdistributed computing andparallel computing,whereby a 'super and virtual computer' is composed of a clusterof networked,loosely coupled computers acting in concert to perform very large tasks"

4. Mainframe powerful computers used mainly by large organizations for critical

applications, typically bulk data processing such ascensus, industry and consumer

statistics, enterprise resource planning, and financialtransaction processing.[11]5. Utility computing the "packaging ofcomputing resources, such as computation

and storage, as a metered service similar to a traditionalpublic utility, such as

electricity";[12]6. Peer-to-peer (disambiguation) systems in which data transfer utilizes the shared

resources of every system attached to the Intranet, setup for a specific task or

purpose (ie: BitTorrent (protocol) as one example of many which exists.)

[edit] Characteristics

In general, cloud computing customers do not own the physical infrastructure, instead

avoiding capital expenditure by renting usage from a third-party provider. They consumeresources as a service and pay only for resources that they use. Many cloud-computing

offerings employ the utility computing model, which is analogous to how traditional

utility services (such as electricity) are consumed, whereas others bill on asubscriptionbasis. Sharing "perishable and intangible" computing power among multiple tenants can

improve utilization rates, as servers are not unnecessarily left idle (which can reduce

costs significantly while increasing the speed of application development). A side-effectof this approach is that overall computer usage rises dramatically, as customers do nothave to engineer for peak load limits.[13] In addition, "increased high-speed bandwidth"

makes it possible to receive the same response times from centralized infrastructure at

other sites[14].

[edit] Economics
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Cloud computing users can avoid capital expenditure(CapEx) on hardware, software,

and services when they pay a provider only for what they use. Consumption is usually

billed on a utility(resources consumed, like electricity) orsubscription (time-based, like anewspaper) basis with little or no upfront cost. Other benefits of this time sharing-style

approach are lowbarriers to entry, shared infrastructure and costs, low management

overhead, and immediate access to a broad range of applications. In general, users canterminate the contract at any time (thereby avoiding return on investmentrisk and

uncertainty), and the services are often covered by service level agreements (SLAs) with

financial penalties.[15][16]

According toNicholas Carr, the strategic importance ofinformation technologyisdiminishing as it becomes standardized and less expensive. He argues that the cloud

computingparadigm shift is similar to the displacement ofelectricity generators by

electricity grids early in the 20th century.[17]

Although companies might be able to save on upfront capital expenditures, they might

not save much and might actually pay more for operating expenses. In situations wherethe capital expense would be relatively small, or where the organization has more

flexibility in their capital budget than their operating budget, the cloud model might notmake great fiscal sense. Other factors impacting the scale of any potential cost savings

include the efficiency of a companys data center as compared to the cloud vendors, the

company's existing operating costs, the level of adoption of cloud computing, and thetype of functionality being hosted in the cloud.[18][19]

[edit] Architecture

Cloud computing sample architecture

Cloud architecture,[20] the systems architecture of thesoftware systems involved in thedelivery ofcloud computing, typically involves multiple cloud components

communicating with each other overapplication programming interfaces, usually web

services.[21]This resembles the Unix philosophy of having multiple programs each doing

one thing well and working together over universal interfaces. Complexity is controlledand the resulting systems are more manageable than theirmonolithiccounterparts.

[edit] History

The underlying concept of cloud computing dates back to1960, whenJohn McCarthyopined that "computation may someday be organized as apublic utility"; indeed it shares

characteristics with service bureausthat date back to the 1960s. The actual term "cloud"

borrows from telephony in that telecommunications companies, who until the 1990s

primarily offered dedicated point-to-point data circuits, began offeringVirtual PrivateNetwork(VPN) services with comparable quality of service but at a much lower cost. By

switching traffic to balance utilization as they saw fit they were able to utilise their
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overall network bandwidth more effectively. The cloud symbol was used to denote the

demarcation point between that which was the responsibility of the provider from that of

the user. Cloud computing extends this boundary to cover servers as well as the networkinfrastructure.[22]

Amazon played a key role in the development of cloud computing by modernizing theirdata centers after thedot-com bubble, which, like most computer networks, were using as

little as 10% of their capacity at any one time just to leave room for occasional spikes.Having found that the new cloud architecture resulted in significant internal efficiency

improvements whereby small, fast-moving "two-pizza teams" could add new features

faster and easier, Amazon started providing access to their systems throughAmazon WebServices on a utility computing basis in2005.[23]

In 2007, Google,IBM, and a number of universities embarked on a large scale cloud

computing research project.[24]By mid-2008, Gartner saw an opportunity for cloud

computing "to shape the relationship among consumers of IT services, those who use IT

services and those who sell them",

[25]

and observed that "[o]rganisations are switchingfrom company-owned hardware and software assets to per-use service-based models" so

that the "projected shift to cloud computing ... will result in dramatic growth in ITproducts in some areas and significant reductions in other areas." [26]

[edit] Key features

Agility improves with users' ability to rapidly and inexpensively re-provision

technological infrastructure resources.[27]

Cost is claimed to be greatly reduced andcapital expenditureis converted to

operational expenditure[28] . This ostensibly lowersbarriers to entry, as

infrastructure is typically provided by a third-party and does not need to bepurchased for one-time or infrequent intensive computing tasks. Pricing on a

utility computing basis is fine-grained with usage-based options and fewer IT

skills are required for implementation (in-house).[29]

Device and location independence[30] enable users to access systems using a webbrowser 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.[29]

Multi-tenancy enables sharing of resources and costs across a large pool of users

thus allowing for:

o Centralization of infrastructure in locations with lower costs (such as real

estate, electricity, etc.)o Peak-load capacity increases (users need not engineer for highest

possible load-levels)o Utilization and efficiency improvements for systems that are often only

1020% utilized.[23]

Reliability improves through the use of multiple redundant sites, which makescloud computing suitable forbusiness continuity and disaster recovery.[31]
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Nonetheless, many major cloud computing services have suffered outages, and IT

and business managers can at times do little when they are affected.[32][33]

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. Performanceis monitored, and consistent and loosely coupled

architectures are constructed using web services as the system interface.[29]

One ofthe most important new methods for overcoming performance bottlenecks for a

large class of applications is data parallel programming on a distributed data grid.[34]

Security could improve due to centralization of data[35], 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 [36]. Security is often as

good as or better than under traditional systems, in part because providers are ableto devote resources to solving security issues that many customers cannot afford.[37] Providers typically log accesses, but accessing theaudit 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 cloud computing applications are easier to maintain, since they

don't have to be installed on each user's computer. They are easier to support andto improve since the changes reach the clients instantly.

Metering cloud computing resources usage should be measurable and should be

metered per client and application on daily, weekly, monthly, and annual basis.

This will enable clients on choosing the vendor cloud on cost and reliability(QoS).

[edit] Layers

[edit] Client

See also: Category:Cloud clients

A cloud clientconsists ofcomputer hardware and/orcomputer softwarethat relies oncloud 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

somecomputers, phones and other devices, operating systems andbrowsers.[38][39][40][41][42]

[edit] Application

See also: Category:Cloud applications

Cloud application services or "Software as a Service (SaaS)" deliversoftware as a service

over the Internet, eliminating the need to install and run the application on the customer'sown computers and simplifying maintenance and support. Key characteristics include:[43]
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Network-based access to, and management of, commercially available (i.e., not

custom) software

Activities that are managed from central locations rather than at each customer'ssite, enabling customers to access applications remotely via the Web

Application delivery that typically is closer to a one-to-many model (single

instance, multi-tenant architecture) than to a one-to-one model, includingarchitecture, pricing, partnering, and management characteristics

Centralized feature updating, which obviates the need for downloadable patches

and upgrades.

[edit] Platform

See also: Category:Cloud platforms

Cloud platform services or "Platform as a Service (PaaS)" deliver a computing platformand/orsolution stackas a service, often consuming cloud infrastructure and sustaining

cloud applications. It facilitates deployment of applications without the cost andcomplexity of buying and managing the underlying hardware and software layers.[44][45]

[edit] Infrastructure

See also: Category:Cloud infrastructure

Cloud infrastructure services or "Infrastructure as a Service (IaaS)" delivers computer

infrastructure, typically aplatform virtualizationenvironment as a service. Rather thanpurchasing servers, software, data center space or network equipment, clients instead buy

those resources as a fully outsourced service. The service is typically billed on autility

computing basis and amount of resources consumed (and therefore the cost) will typicallyreflect the level of activity. It is an evolution ofvirtual private serverofferings.[46]

[edit] Server

Theservers layer consists ofcomputer hardwareand/orcomputer software products that

are specifically designed for the delivery of cloud services, including multi-core

processors, cloud-specific operating systems and combined offerings.[38][47][48][49]

[edit] Deployment models

Cloud computing types

Public cloudorexternal clouddescribes cloud computing in the traditional mainstreamsense, whereby resources are dynamically provisioned on a fine-grained, self-service
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basis over the Internet, via web applications/web services, from an off-site third-party

provider whoshares resources and bills on a fine-grainedutility computing basis.[29]

[edit] Community cloud

A community cloudmay be established where several organizations have similarrequirements and seek to share infrastructure so as to realize some of the benefits ofcloud computing. With the costs spread over fewer users than apublic 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 ofcommunity cloudincludeGoogle's "Gov Cloud".[50]

[edit] Hybrid cloud

A hybrid cloudenvironment consisting of multiple internal and/or external providers[51]

"will be typical for most enterprises".[52] By integrating multiple cloud services users may

be able to ease the transition topublic cloudservices while avoiding issues such as PCIcompliance.[53]

Another perspective on deploying a web application in the cloud is using Hybrid Web

Hosting, where the hosting infrastructure is a mix between Cloud Hostingfor the web

server, and Managed dedicated serverfor the database server.[54]

[edit] Private cloud

Private cloudand internal cloudare neologismsthat some vendors have recently used todescribe offerings that emulate cloud computing on private networks. These (typically

virtualisationautomation) products claim to "deliver some benefits of cloud computingwithout the pitfalls", capitalising on data security, corporate governance, and reliabilityconcerns. They have been criticized on the basis that users "still have to buy, build, and

manage them" and as such do not benefit from lower up-front capital costs and less

hands-on management[52], essentially "[lacking] the economic model that makes cloudcomputing such an intriguing concept".[55][56]

[edit] Issues

[edit] Privacy

The Cloud model has been criticized by privacy advocates for the greater ease in which

the companies hosting the Cloud services control, and thus, can monitor at will, lawfully

or unlawfully, the communication and data stored between the user and the hostcompany. Instances such as the secretNSAprogram, working with AT&T, and Verizon,

which recorded over 10 million phone calls between American citizens, causes

uncertainty among privacy advocates, and the greater powers it gives to

telecommunication companies to monitor user activity.[57]While there have been efforts
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(such as US-EU Safe Harbor) to "harmonise" the legal environment, providers such as

Amazon still cater to major markets (typically the United Statesand the European Union)

by deploying local infrastructure and allowing customers to select "availability zones."[58]

[edit] Compliance

In order to obtain compliance with regulations including FISMA, HIPAA and SOX in theUS, the Data Protection Directive in theEU and the credit card industry's PCI DSS, users

may have to adopt community orhybriddeployment modes which are typically more

expensive and may offer restricted benefits. This is how Googleis able to "manage andmeet additional government policy requirements beyond FISMA"[59][60] and Rackspace

Cloud are able to claim PCI compliance.[61]

Many providers also obtain SAS 70 Type II certification (e.g. Amazon[62], Google[63] and

Microsoft[64]), but this has been criticised on the grounds that the hand-picked set of goalsand standards determined by the auditor and the auditee are often not disclosed and can

vary widely.[65]

Providers typically make this information available on request, undernon-disclosure agreement.[66]

[edit] Legal

In March 2007, Dell applied totrademarkthe term "cloud computing" (U.S. Trademark

77,139,082) in the United States. The "Notice of Allowance" the company received inJuly 2008 was cancelled in August, resulting in a formal rejection of the trademark

application less than a week later.

Since 2007, the number of trademark filings covering cloud computing brands, goods and

services has increased at an almost exponential rate.[67]

As companies sought to betterposition themselves for cloud computing branding and marketing efforts, cloud

computing trademark filings increased by 483% between 2008 and 2009. [68] In 2009, 116

cloud computing trademarks were filed, and trademark analysts predict that over 500such marks could be filed during 2010. [69]

[edit] Open source

Open standardsare critical to the growth of cloud computing, andopen source software

has provided the foundation for many cloud computing implementations.[70] In November

2007, the Free Software Foundation released the Affero General Public License, a

version ofGPLv3 intended to close a perceived legal loophole associated with freesoftwaredesigned to be run over a network.[71]

[edit] Open standards

See also: Category:Cloud standards
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Most cloud providers expose APIs which are typically well-documented (often under a

Creative Commons license[72]) however also unique to their implementation and thus not

interoperable. Some vendors have adopted others' APIs[73] and there are a number ofopenstandardsunder development, including theOGF'sOpen Cloud Computing Interface.

The Open Cloud Consortium (OCC) [74] is working to develop consensus on early cloud

computing standards and practices.

[edit] Security

The relative security of cloud computing services is a contentious issue which may bedelaying its adoption.[75]Some argue that customer data is more secure when managed

internally, while others argue that cloud providers have a strong incentive to maintain

trust and as such employ a higher level of security.[76]

[edit] Sustainability

Although cloud computing is often assumed to be a form of "green computing", there isas of yet no published study to substantiate this assumption.

Comparisons

Cloud computing derives characteristics from, but should not be confused with:

1. Autonomic computing "computer systems capable ofself-management".[9]2. Client-server Client-server computing refers broadly to any distributed

applicationthat distinguishes between service providers (servers) and service

requesters (clients).[10]

3. Grid computing "a form ofdistributed computing andparallel computing,whereby a 'super and virtual computer' is composed of a clusterof networked,

loosely coupled computers acting in concert to perform very large tasks"4. Mainframe powerful computers used mainly by large organizations for critical

applications, typically bulk data processing such ascensus, industry and consumer

statistics, enterprise resource planning, and financialtransaction processing.[11]

5. Utility computing the "packaging ofcomputing resources, such as computationand storage, as a metered service similar to a traditionalpublic utility, such as

electricity";[12]

6. Peer-to-peer (disambiguation) systems in which data transfer utilizes the sharedresources of every system attached to the Intranet, setup for a specific task or

purpose (ie: BitTorrent (protocol) as one example of many which exists.)

[edit] Characteristics

In general, cloud computing customers do not own the physical infrastructure, instead

avoiding capital expenditure by renting usage from a third-party provider. They consume

resources as a service and pay only for resources that they use. Many cloud-computingofferings employ the utility computing model, which is analogous to how traditional
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ote-10%23cite_note-10http://en.wikipedia.org/wiki/Utility_computinghttp://en.wikipedia.org/wiki/Computational_resourcehttp://en.wikipedia.org/wiki/Public_utilityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-It.27s_probable_that_you.E2.80.99ve_misunderstood_.E2.80.9CCloud_Computing.E2.80.9D_till_now-11%23cite_note-It.27s_probable_that_you.E2.80.99ve_misunderstood_.E2.80.9CCloud_Computing.E2.80.9D_till_now-11http://en.wikipedia.org/wiki/Peer-to-peer_(disambiguation)http://en.wikipedia.org/wiki/Intranethttp://en.wikipedia.org/wiki/BitTorrent_(protocol)http://en.wikipedia.org/w/index.php?title=Cloud_computing&action=edit&section=2http://en.wikipedia.org/wiki/Capital_expenditurehttp://en.wikipedia.org/w/index.php?title=Everything_as_a_service&action=edit&redlink=1http://en.wikipedia.org/wiki/Utility_computing


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utility services (such as electricity) are consumed, whereas others bill on asubscription

basis. Sharing "perishable and intangible" computing power among multiple tenants can

improve utilization rates, as servers are not unnecessarily left idle (which can reducecosts significantly while increasing the speed of application development). A side-effect

of this approach is that overall computer usage rises dramatically, as customers do not

have to engineer for peak load limits.[13]

In addition, "increased high-speed bandwidth"makes it possible to receive the same response times from centralized infrastructure at

other sites[14].

[edit] Economics

Cloud computing users can avoid capital expenditure(CapEx) on hardware, software,

and services when they pay a provider only for what they use. Consumption is usuallybilled on a utility(resources consumed, like electricity) orsubscription (time-based, like a

newspaper) basis with little or no upfront cost. Other benefits of this time sharing-style

approach are lowbarriers to entry, shared infrastructure and costs, low management

overhead, and immediate access to a broad range of applications. In general, users canterminate the contract at any time (thereby avoiding return on investmentrisk and

uncertainty), and the services are often covered by service level agreements (SLAs) with

financial penalties.[15][16]

According toNicholas Carr, the strategic importance ofinformation technologyisdiminishing as it becomes standardized and less expensive. He argues that the cloud

computingparadigm shift is similar to the displacement ofelectricity generators by

electricity grids early in the 20th century.[17]

Although companies might be able to save on upfront capital expenditures, they might

not save much and might actually pay more for operating expenses. In situations wherethe capital expense would be relatively small, or where the organization has more

flexibility in their capital budget than their operating budget, the cloud model might notmake great fiscal sense. Other factors impacting the scale of any potential cost savings

include the efficiency of a companys data center as compared to the cloud vendors, the

company's existing operating costs, the level of adoption of cloud computing, and thetype of functionality being hosted in the cloud.[18][19]

[edit] Architecture

Cloud computing sample architecture

Cloud architecture,[20] the systems architecture of thesoftware systems involved in the

delivery ofcloud computing, typically involves multiple cloud components

communicating with each other overapplication programming interfaces, usually web

services.[21]This resembles the Unix philosophy of having multiple programs each doing
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one thing well and working together over universal interfaces. Complexity is controlled

and the resulting systems are more manageable than theirmonolithiccounterparts.

[edit] History

The underlying concept of cloud computing dates back to1960, whenJohn McCarthyopined that "computation may someday be organized as apublic utility"; indeed it shares

characteristics with service bureausthat date back to the 1960s. The actual term "cloud"

borrows from telephony in that telecommunications companies, who until the 1990sprimarily offered dedicated point-to-point data circuits, began offeringVirtual Private

Network(VPN) services with comparable quality of service but at a much lower cost. By

switching traffic to balance utilization as they saw fit they were able to utilise theiroverall network bandwidth more effectively. The cloud symbol was used to denote the

demarcation point between that which was the responsibility of the provider from that of

the user. Cloud computing extends this boundary to cover servers as well as the networkinfrastructure.[22]

Amazon played a key role in the development of cloud computing by modernizing their

data centers after thedot-com bubble, which, like most computer networks, were using as

little as 10% of their capacity at any one time just to leave room for occasional spikes.Having found that the new cloud architecture resulted in significant internal efficiency

improvements whereby small, fast-moving "two-pizza teams" could add new features

faster and easier, Amazon started providing access to their systems throughAmazon Web

Services on a utility computing basis in2005.[23]

In 2007, Google,IBM, and a number of universities embarked on a large scale cloud

computing research project.[24]By mid-2008, Gartner saw an opportunity for cloud

computing "to shape the relationship among consumers of IT services, those who use ITservices and those who sell them",[25] and observed that "[o]rganisations are switching

from company-owned hardware and software assets to per-use service-based models" so

that the "projected shift to cloud computing ... will result in dramatic growth in IT

products in some areas and significant reductions in other areas." [26]

[edit] Key features

Agility improves with users' ability to rapidly and inexpensively re-provision

technological infrastructure resources.[27]

Cost is claimed to be greatly reduced andcapital expenditureis converted tooperational expenditure[28] . This ostensibly lowersbarriers 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 autility computing basis is fine-grained with usage-based options and fewer IT

skills are required for implementation (in-house).[29]

Device and location independence[30] enable users to access systems using a webbrowser regardless of their location or what device they are using (e.g., PC,
http://en.wikipedia.org/wiki/Monolithic_systemhttp://en.wikipedia.org/wiki/Monolithic_systemhttp://en.wikipedia.org/w/index.php?title=Cloud_computing&action=edit&section=5http://en.wikipedia.org/wiki/1960http://en.wikipedia.org/wiki/1960http://en.wikipedia.org/wiki/John_McCarthy_(computer_scientist)http://en.wikipedia.org/wiki/John_McCarthy_(computer_scientist)http://en.wikipedia.org/wiki/Public_utilityhttp://en.wikipedia.org/wiki/Service_bureauhttp://en.wikipedia.org/wiki/Service_bureauhttp://en.wikipedia.org/wiki/Telephonyhttp://en.wikipedia.org/wiki/Virtual_Private_Networkhttp://en.wikipedia.org/wiki/Virtual_Private_Networkhttp://en.wikipedia.org/wiki/Virtual_Private_Networkhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-21%23cite_note-21http://en.wikipedia.org/wiki/Amazon.comhttp://en.wikipedia.org/wiki/Data_centerhttp://en.wikipedia.org/wiki/Dot-com_bubblehttp://en.wikipedia.org/wiki/Dot-com_bubblehttp://en.wikipedia.org/wiki/Dot-com_bubblehttp://en.wikipedia.org/wiki/Computer_networkshttp://en.wikipedia.org/wiki/Computer_networkshttp://en.wikipedia.org/wiki/Amazon_Web_Serviceshttp://en.wikipedia.org/wiki/Amazon_Web_Serviceshttp://en.wikipedia.org/wiki/Amazon_Web_Serviceshttp://en.wikipedia.org/wiki/Utility_computinghttp://en.wikipedia.org/wiki/2005http://en.wikipedia.org/wiki/2005http://en.wikipedia.org/wiki/Cloud_computing#cite_note-amazon-22%23cite_note-amazon-22http://en.wikipedia.org/wiki/Cloud_computing#cite_note-amazon-22%23cite_note-amazon-22http://en.wikipedia.org/wiki/2007http://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/IBMhttp://en.wikipedia.org/wiki/IBMhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-23%23cite_note-23http://en.wikipedia.org/wiki/Cloud_computing#cite_note-23%23cite_note-23http://en.wikipedia.org/wiki/Cloud_computing#cite_note-23%23cite_note-23http://en.wikipedia.org/wiki/Cloud_computing#cite_note-24%23cite_note-24http://en.wikipedia.org/wiki/Cloud_computing#cite_note-24%23cite_note-24http://en.wikipedia.org/wiki/Cloud_computing#cite_note-25%23cite_note-25http://en.wikipedia.org/w/index.php?title=Cloud_computing&action=edit&section=6http://en.wikipedia.org/wiki/Agilityhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-26%23cite_note-26http://en.wikipedia.org/wiki/Cloud_computing#cite_note-26%23cite_note-26http://en.wikipedia.org/wiki/Cloud_computing#cite_note-26%23cite_note-26http://en.wikipedia.org/wiki/Costhttp://en.wikipedia.org/wiki/Capital_expenditurehttp://en.wikipedia.org/wiki/Capital_expenditurehttp://en.wikipedia.org/wiki/Capital_expenditurehttp://en.wikipedia.org/wiki/Operational_expenditurehttp://en.wikipedia.org/wiki/Operational_expenditurehttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-27%23cite_note-27http://en.wikipedia.org/wiki/Cloud_computing#cite_note-27%23cite_note-27http://en.wikipedia.org/wiki/Cloud_computing#cite_note-27%23cite_note-27http://en.wikipedia.org/wiki/Barriers_to_entryhttp://en.wikipedia.org/wiki/Utility_computinghttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-idc-28%23cite_note-idc-28http://en.wikipedia.org/wiki/Cloud_computing#cite_note-idc-28%23cite_note-idc-28http://en.wikipedia.org/wiki/Cloud_computing#cite_note-idc-28%23cite_note-idc-28http://en.wikipedia.org/wiki/Device_independencehttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-yarmis-29%23cite_note-yarmis-29http://en.wikipedia.org/wiki/Monolithic_systemhttp://en.wikipedia.org/w/index.php?title=Cloud_computing&action=edit&section=5http://en.wikipedia.org/wiki/1960http://en.wikipedia.org/wiki/John_McCarthy_(computer_scientist)http://en.wikipedia.org/wiki/Public_utilityhttp://en.wikipedia.org/wiki/Service_bureauhttp://en.wikipedia.org/wiki/Telephonyhttp://en.wikipedia.org/wiki/Virtual_Private_Networkhttp://en.wikipedia.org/wiki/Virtual_Private_Networkhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-21%23cite_note-21http://en.wikipedia.org/wiki/Amazon.comhttp://en.wikipedia.org/wiki/Data_centerhttp://en.wikipedia.org/wiki/Dot-com_bubblehttp://en.wikipedia.org/wiki/Computer_networkshttp://en.wikipedia.org/wiki/Amazon_Web_Serviceshttp://en.wikipedia.org/wiki/Amazon_Web_Serviceshttp://en.wikipedia.org/wiki/Utility_computinghttp://en.wikipedia.org/wiki/2005http://en.wikipedia.org/wiki/Cloud_computing#cite_note-amazon-22%23cite_note-amazon-22http://en.wikipedia.org/wiki/2007http://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/IBMhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-23%23cite_note-23http://en.wikipedia.org/wiki/Cloud_computing#cite_note-24%23cite_note-24http://en.wikipedia.org/wiki/Cloud_computing#cite_note-25%23cite_note-25http://en.wikipedia.org/w/index.php?title=Cloud_computing&action=edit&section=6http://en.wikipedia.org/wiki/Agilityhttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-26%23cite_note-26http://en.wikipedia.org/wiki/Costhttp://en.wikipedia.org/wiki/Capital_expenditurehttp://en.wikipedia.org/wiki/Operational_expenditurehttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-27%23cite_note-27http://en.wikipedia.org/wiki/Barriers_to_entryhttp://en.wikipedia.org/wiki/Utility_computinghttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-idc-28%23cite_note-idc-28http://en.wikipedia.org/wiki/Device_independencehttp://en.wikipedia.org/wiki/Cloud_computing#cite_note-yarmis-29%23cite_note-yarmis-29


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mobile). As infrastructure is off-site (typically provided by a third-party) and

accessed via the Internet, users can connect from anywhere.[29]

Multi-tenancy enables sharing of resources and costs across a large pool of usersthus allowing for:

o Centralization of infrastructure in locations with lower costs (such as real

estate, electricity, etc.)o Peak-load capacity increases (users need not engineer for highest

possible load-levels)

o Utilization and efficiency improvements for systems that are often only

1020% utilized.[23]

Reliability improves through the use of multiple redundant sites, which makes

cloud computing suitable forbusiness continuity and disaster recovery.[31]

Nonetheless, many major cloud computing services have suffered outages, and IT

and business managers can at times do little when they are affected.[32][33]

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. Performanceis monitored, and consistent and loosely coupledarchitectures are constructed using web services as the system interface.[29] One of

the most important new methods for overcoming performance bottlenecks for alarge class of applications is data parallel programming on a distributed data grid.[34]

Security could improve due to centralization of data[35], 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 [36]. Security is often as

good as or better than under traditional systems, in part because providers are ableto devote resources to solving security issues that many customers cannot afford.[37] Providers typically log accesses, but accessing theaudit logs themselves can be

difficult or impossible. Furthermore, the complexity of security is greatlyincreased when data is distributed over a wider area and / or number of devices. Maintenance cloud computing applications are easier to maintain, 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 cloud computing resources usage should be measurable and should be

metered per client and application on daily, weekly, monthly, and annual basis.

This will enable clients on choosing the vendor cloud on cost and reliability(QoS).

[edit] Layers

[edit] Client

See also: Category:Cloud clients
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cloud computing is internet

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