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Cloud computing metaphor: For a user, the network elementsrepresenting the provider-rendered services are invisible, as if ob-scured by a cloud.

Cloud computing is a model for enabling ubiquitous,convenient, on-demand access to a shared pool of con-figurable computing resources.[1] Cloud computing andstorage solutions provide users and enterprises with var-ious capabilities to store and process their data in third-party data centers.[2] It relies on sharing of resources toachieve coherence and economies of scale, similar to autility (like the electricity grid) over a network.[3] At thefoundation of cloud computing is the broader concept ofconverged infrastructure and shared services.Cloud computing, or in simpler shorthand just “thecloud”, also focuses on maximizing the effectiveness ofthe shared resources. Cloud resources are usually not onlyshared by multiple users but are also dynamically reallo-cated per demand. This can work for allocating resourcesto users. For example, a cloud computer facility thatserves European users during European business hourswith a specific application (e.g., email) may reallocatethe same resources to serve North American users duringNorth America’s business hours with a different applica-tion (e.g., a web server). This approach helps maximizethe use of computing power while reducing the overallcost of resources by using less power, air conditioning,rack space, etc. to maintain the system. With cloud com-puting, multiple users can access a single server to re-trieve and update their data without purchasing licensesfor different applications.The term “moving to cloud” also refers to an organiza-tion moving away from a traditional CAPEX model (buy

the dedicated hardware and depreciate it over a period oftime) to the OPEX model (use a shared cloud infrastruc-ture and pay as one uses it).Proponents claim that cloud computing allows compa-nies to avoid upfront infrastructure costs, and focus onprojects that differentiate their businesses instead of oninfrastructure.[4] Proponents also claim that cloud com-puting allows enterprises to get their applications up andrunning faster, with improved manageability and lessmaintenance, and enables IT to more rapidly adjust re-sources to meet fluctuating and unpredictable businessdemand.[4][5][6] Cloud providers typically use a “pay asyou go” model. This can lead to unexpectedly highcharges if administrators do not adapt to the cloud pricingmodel.[7]

The present availability of high-capacity networks, low-cost computers and storage devices as well as thewidespread adoption of hardware virtualization, service-oriented architecture, and autonomic and utility com-puting have led to a growth in cloud computing.[8][9][10]Companies can scale up as computing needs increase andthen scale down again as demands decrease.Cloud vendors are experiencing growth rates of 50% perannum.[11]

1 History of cloud computing

1.1 Origin of the term

The origin of the term cloud computing is unclear. Theexpression cloud is commonly used in science to describea large agglomeration of objects that visually appear froma distance as a cloud and describes any set of things whosedetails are not inspected further in a given context.[12] An-other explanation is that the old programs that drew net-work schematics surrounded the icons for servers with acircle, and a cluster of servers in a network diagram hadseveral overlapping circles, which resembled a cloud.[13]

In analogy to above usage the word cloud was used asa metaphor for the Internet and a standardized cloud-like shape was used to denote a network on telephonyschematics and later to depict the Internet in computernetwork diagrams. With this simplification, the implica-tion is that the specifics of how the end points of a networkare connected are not relevant for the purposes of under-standing the diagram. The cloud symbol was used to rep-resent networks of computing equipment in the original

1

2 2 SIMILAR CONCEPTS

ARPANET by as early as 1977,[14] and the CSNET by1981[15]—both predecessors to the Internet itself.References to cloud computing in its modern sense ap-peared as early as 1996, with the earliest known mentionin a Compaq internal document.[16]

The popularization of the term can be traced to 2006when Amazon.com introduced the Elastic ComputeCloud.[17]

1.2 The 1970s

During the mid-1970s, time-sharing was popularlyknown as RJE (Remote Job Entry); this terminology wasmostly associated with large vendors such as IBM andDEC. IBM developed the VM Operating System (firstreleased in 1972) to provide time-sharing services viavirtual machines.

1.3 The 1990s

In the 1990s, telecommunications companies, who previ-ously offered primarily dedicated point-to-point data cir-cuits, began offering virtual private network (VPN) ser-vices with comparable quality of service, but at a lowercost. By switching traffic as they saw fit to balance serveruse, they could use overall network bandwidth more ef-fectively. They began to use the cloud symbol to denotethe demarcation point between what the provider was re-sponsible for and what users were responsible for. Cloudcomputing extends this boundary to cover all servers aswell as the network infrastructure.[18]

As computers became more prevalent, scientists andtechnologists explored ways to make large-scale com-puting power available to more users through time-sharing. They experimented with algorithms to optimizethe infrastructure, platform, and applications to prioritizeCPUs and increase efficiency for end users.[19]

1.4 The New Millennium: 2000s

Since 2000 cloud computing has come into existence.In early 2008, NASA's OpenNebula, enhanced in theRESERVOIR European Commission-funded project,became the first open-source software for deployingprivate and hybrid clouds, and for the federation ofclouds.[20] In the same year, efforts were focused onproviding quality of service guarantees (as required byreal-time interactive applications) to cloud-based in-frastructures, in the framework of the IRMOS Euro-pean Commission-funded project, resulting in a real-timecloud environment.[21] By mid-2008, Gartner saw an op-portunity for cloud computing “to shape the relation-ship among consumers of IT services, those who use ITservices and those who sell them”[22] and observed that

“organizations are switching from company-owned hard-ware and software assets to per-use service-based mod-els” so that the “projected shift to computing ... will resultin dramatic growth in IT products in some areas and sig-nificant reductions in other areas.”[23]

Microsoft Azure became available in late 2008.In July 2010, Rackspace Hosting and NASA jointlylaunched an open-source cloud-software initiative knownas OpenStack. The OpenStack project intended to helporganizations offer cloud-computing services running onstandard hardware. The early code came from NASA’sNebula platform as well as from Rackspace’s Cloud Filesplatform.[24]

OnMarch 1, 2011, IBM announced the IBMSmartCloudframework to support Smarter Planet.[25] Among the var-ious components of the Smarter Computing foundation,cloud computing is a critical piece.On June 7, 2012, Oracle announced the Oracle Cloud.[26]While aspects of the Oracle Cloud are still in develop-ment, this cloud offering is poised to be the first to pro-vide users with access to an integrated set of IT solutions,including the Applications (SaaS), Platform (PaaS), andInfrastructure (IaaS) layers.[27][28][29]

2 Similar concepts

Cloud computing is the result of the evolution and adop-tion of existing technologies and paradigms. The goal ofcloud computing is to allow users to take benefit from allof these technologies, without the need for deep knowl-edge about or expertise with each one of them. The cloudaims to cut costs, and helps the users focus on their corebusiness instead of being impeded by IT obstacles.[30]

The main enabling technology for cloud computing isvirtualization. Virtualization software separates a phys-ical computing device into one or more “virtual” devices,each of which can be easily used and managed to per-form computing tasks. With operating system–level vir-tualization essentially creating a scalable system of mul-tiple independent computing devices, idle computing re-sources can be allocated and used more efficiently. Vir-tualization provides the agility required to speed up IToperations, and reduces cost by increasing infrastructureutilization. Autonomic computing automates the pro-cess through which the user can provision resources on-demand. By minimizing user involvement, automationspeeds up the process, reduces labor costs and reducesthe possibility of human errors.[30]

Users routinely face difficult business problems. Cloudcomputing adopts concepts from Service-oriented Archi-tecture (SOA) that can help the user break these problemsinto services that can be integrated to provide a solution.Cloud computing provides all of its resources as services,and makes use of the well-established standards and best

3

practices gained in the domain of SOA to allow globaland easy access to cloud services in a standardized way.Cloud computing also leverages concepts from utilitycomputing to provide metrics for the services used. Suchmetrics are at the core of the public cloud pay-per-usemodels. In addition, measured services are an essentialpart of the feedback loop in autonomic computing, allow-ing services to scale on-demand and to perform automaticfailure recovery.Cloud computing is a kind of grid computing; it hasevolved by addressing the QoS (quality of service) andreliability problems. Cloud computing provides the toolsand technologies to build data/compute intensive parallelapplications with much more affordable prices comparedto traditional parallel computing techniques.[30]

Cloud computing shares characteristics with:

• Client–server model — Client–server computingrefers broadly to any distributed application that dis-tinguishes between service providers (servers) andservice requestors (clients).[31]

• Grid computing — “A form of distributed and par-allel computing, whereby a 'super and virtual com-puter' is composed of a cluster of networked, looselycoupled computers acting in concert to perform verylarge tasks.”

• Mainframe computer — Powerful computers usedmainly by large organizations for critical applica-tions, typically bulk data processing such as: census;industry and consumer statistics; police and secretintelligence services; enterprise resource planning;and financial transaction processing.

• Utility computing — The “packaging of computingresources, such as computation and storage, as a me-tered service similar to a traditional public utility,such as electricity.”[32][33]

• Peer-to-peer — A distributed architecture withoutthe need for central coordination. Participants areboth suppliers and consumers of resources (in con-trast to the traditional client–server model).

3 Characteristics

Cloud computing exhibits the following key characteris-tics:

• Agility improves with users’ ability to re-provisiontechnological infrastructure resources.

• Cost reductions claimed by cloud providers. Apublic-cloud delivery model converts capital expen-diture to operational expenditure.[34] This purport-edly lowers barriers to entry, as infrastructure is typ-ically provided by a third party and does not need

to be purchased for one-time or infrequent inten-sive computing tasks. Pricing on a utility computingbasis is fine-grained, with usage-based options andfewer IT skills are required for implementation (in-house).[35] The e-FISCAL project’s state-of-the-artrepository[36] contains several articles looking intocost aspects in more detail, most of them conclud-ing that costs savings depend on the type of activitiessupported and the type of infrastructure available in-house.

• Device and location independence[37] enable usersto access systems using a web browser regardless oftheir location or what device they use (e.g., PC, mo-bile phone). As infrastructure is off-site (typicallyprovided by a third-party) and accessed via the In-ternet, users can connect from anywhere.[35]

• Maintenance of cloud computing applications iseasier, because they do not need to be installed oneach user’s computer and can be accessed from dif-ferent places.

• Multitenancy enables sharing of resources andcosts across a large pool of users thus allowing for:

• centralization of infrastructure in locationswith lower costs (such as real estate, electric-ity, etc.)

• peak-load capacity increases (users need notengineer for highest possible load-levels)

• utilisation and efficiency improvementsfor systems that are often only 10–20%utilised.[38][39]

• Performance is monitored, and consistent andloosely coupled architectures are constructed usingweb services as the system interface.[35][40][41]

• Productivitymay be increased when multiple userscan work on the same data simultaneously, ratherthan waiting for it to be saved and emailed. Timemay be saved as information does not need to bere-entered when fields are matched, nor do usersneed to install application software upgrades to theircomputer.[42]

• Reliability improves with the use ofmultiple redun-dant sites, which makes well-designed cloud com-puting suitable for business continuity and disasterrecovery.[43]

• Scalability and elasticity via dynamic (“on-demand”) provisioning of resources on a fine-grained, self-service basis in near real-time[44][45](Note, the VM startup time varies by VM type, lo-cation, OS and cloud providers[44]), without usershaving to engineer for peak loads.[46][47][48]

4 4 SERVICE MODELS

• Security can improve due to centralization of data,increased security-focused resources, etc., but con-cerns can persist about loss of control over certainsensitive data, and the lack of security for storedkernels. Security is often as good as or better thanother traditional systems, in part because providersare able to devote resources to solving security is-sues that many customers cannot afford to tackle.[49]However, the complexity of security is greatly in-creased when data is distributed over a wider areaor over a greater number of devices, as well as inmulti-tenant systems shared by unrelated users. Inaddition, user access to security audit logs may bedifficult or impossible. Private cloud installationsare in part motivated by users’ desire to retain con-trol over the infrastructure and avoid losing controlof information security.

The National Institute of Standards and Technology'sdefinition of cloud computing identifies “five essentialcharacteristics":

On-demand self-service. A consumer canunilaterally provision computing capabilities,such as server time and network storage, asneeded automatically without requiring humaninteraction with each service provider.

Broad network access. Capabilities areavailable over the network and accessedthrough standard mechanisms that promoteuse by heterogeneous thin or thick client plat-forms (e.g., mobile phones, tablets, laptops,and workstations).

Resource pooling. The provider’s comput-ing resources are pooled to serve multiple con-sumers using a multi-tenant model, with differ-ent physical and virtual resources dynamicallyassigned and reassigned according to consumerdemand.

Rapid elasticity. Capabilities can be elasti-cally provisioned and released, in some casesautomatically, to scale rapidly outward and in-ward commensurate with demand. To the con-sumer, the capabilities available for provision-ing often appear unlimited and can be appro-priated in any quantity at any time.

Measured service. Cloud systems automat-ically control and optimize resource use byleveraging a metering capability at some levelof abstraction appropriate to the type of ser-vice (e.g., storage, processing, bandwidth, andactive user accounts). Resource usage can bemonitored, controlled, and reported, provid-ing transparency for both the provider and con-sumer of the utilized service.

— National Institute of Standards andTechnology[3]

4 Service models

Though service-oriented architecture advocates “every-thing as a service” (with the acronyms EaaS or XaaSor simply aas),[50] cloud-computing providers offer their“services” according to different models,[3][51] whichhappen to form a stack: infrastructure-, platform- andsoftware-as-a-service.[52]

Cloud-computing layers accessible within a stack

4.1 Infrastructure as a service (IaaS)

See also: Category:Cloud infrastructure

In the most basic cloud-service model - and according tothe IETF (Internet Engineering Task Force) - providersof IaaS offer computers – physical or (more often) vir-tual machines – and other resources. Iaas refers to onlineservices that abstract user from the detail of infrastucturelike physical computing resources, location, data parti-tioning, scaling, security, backup etc. A hypervisor, suchas Xen, Oracle VirtualBox, KVM, VMware ESX/ESXi,or Hyper-V runs the virtual machines as guests. Poolsof hypervisors within the cloud operational system cansupport large numbers of virtual machines and the abil-ity to scale services up and down according to customers’varying requirements. IaaS clouds often offer addi-tional resources such as a virtual-machine disk-image li-brary, raw block storage, file or object storage, firewalls,load balancers, IP addresses, virtual local area networks(VLANs), and software bundles.[53] IaaS-cloud providerssupply these resources on-demand from their large poolsof equipment installed in data centers. For wide-area con-nectivity, customers can use either the Internet or carrierclouds (dedicated virtual private networks).To deploy their applications, cloud users install operating-system images and their application software on the cloudinfrastructure. In this model, the cloud user patches and

5

maintains the operating systems and the application soft-ware. Cloud providers typically bill IaaS services on autility computing basis: cost reflects the amount of re-sources allocated and consumed.[54][55][56][57]

4.2 Platform as a service (PaaS)

Main article: Platform as a serviceSee also: Category:Cloud platforms

PaaS vendors offers a development environment to appli-cation developers.The provider typically develops toolkitand standards for development and channels for distribu-tion and payment.In the PaaSmodels, cloud providers de-liver a computing platform, typically including operatingsystem, programming-language execution environment,database, and web server. Application developers can de-velop and run their software solutions on a cloud platformwithout the cost and complexity of buying and manag-ing the underlying hardware and software layers. Withsome PaaS offers like Microsoft Azure and Google AppEngine, the underlying computer and storage resourcesscale automatically to match application demand so thatthe cloud user does not have to allocate resources manu-ally. The latter has also been proposed by an architectureaiming to facilitate real-time in cloud environments.[58]Even more specific application types can be provided viaPaaS, such as media encoding as provided by services likebitcodin.com[59] or media.io.[60]

Some integration and data management providers havealso embraced specialized applications of PaaS as deliv-ery models for data solutions. Examples include iPaaSand dPaaS. iPaaS (Integration Platform as a Service) en-ables customers to develop, execute and govern integra-tion flows.[61] Under the iPaaS integration model, cus-tomers drive the development and deployment of inte-grations without installing or managing any hardware ormiddleware.[62] dPaaS (Data Platform as a Service) de-livers integration—and data-management—products as afully managed service.[63] Under the dPaaS model, thePaaS provider, not the customer, manages the develop-ment and execution of data solutions by building tai-lored data applications for the customer. dPaaS usersretain transparency and control over data through data-visualization tools.[64]

4.3 Software as a service (SaaS)

Main article: Software as a service

In the software as a service (SaaS) model, users gainaccess to application software and databases. Cloudproviders manage the infrastructure and platforms thatrun the applications. SaaS is sometimes referred to as“on-demand software” and is usually priced on a pay-per-

use basis or using a subscription fee.In the SaaS model, cloud providers install and operateapplication software in the cloud and cloud users accessthe software from cloud clients. Cloud users do not man-age the cloud infrastructure and platform where the ap-plication runs. This eliminates the need to install and runthe application on the cloud user’s own computers, whichsimplifies maintenance and support. Cloud applicationsdiffer from other applications in their scalability—whichcan be achieved by cloning tasks onto multiple virtualmachines at run-time to meet changing work demand.[65]Load balancers distribute the work over the set of virtualmachines. This process is transparent to the cloud user,who sees only a single access-point. To accommodate alarge number of cloud users, cloud applications can bemultitenant, meaning that any machine may serve morethan one cloud-user organization.The pricing model for SaaS applications is typically amonthly or yearly flat fee per user,[66] so prices becomescalable and adjustable if users are added or removed atany point.[67]

Proponents claim that SaaS gives a business the poten-tial to reduce IT operational costs by outsourcing hard-ware and software maintenance and support to the cloudprovider. This enables the business to reallocate IT oper-ations costs away from hardware/software spending andfrom personnel expenses, towards meeting other goals.In addition, with applications hosted centrally, updatescan be released without the need for users to install newsoftware. One drawback of SaaS comes with storing theusers’ data on the cloud provider’s server. As a result,there could be unauthorized access to the data. For thisreason, users are increasingly adopting intelligent third-party key-management systems to help secure their data.

5 Cloud clients

See also: Category:Cloud clients

Users access cloud computing using networked client de-vices, such as desktop computers, laptops, tablets andsmartphones and any Ethernet enabled device such asHome Automation Gadgets. Some of these devices –cloud clients – rely on cloud computing for all or a ma-jority of their applications so as to be essentially uselesswithout it. Examples are thin clients and the browser-based Chromebook. Many cloud applications do not re-quire specific software on the client and instead use aweb browser to interact with the cloud application. WithAjax and HTML5 these Web user interfaces can achievea similar, or even better, look and feel to native appli-cations. Some cloud applications, however, support spe-cific client software dedicated to these applications (e.g.,virtual desktop clients and most email clients). Somelegacy applications (line of business applications that un-

6 6 DEPLOYMENT MODELS

til now have been prevalent in thin client computing) aredelivered via a screen-sharing technology.

5.1 Cloud Provider Interface

A Cloud Provider Interface (CPI) provide an abstrac-tion from an underlying IaaS by defining a set of functionsfor managing virtual machines life-cycle in which mightrun an elastic service.References:

• http://france.emc.com/collateral/white-paper/h12825-cloud-foundry-paas-vblock-wp.pdf -EMC white paper on Cloud Foundry

• https://bosh.io/ - BOSH, an open-source CPI formultiples PaaS

6 Deployment models

The Cloud

P ublic/

Exter nal

P rivate/

Inter nal

Hybrid

Off P r emises / Thir d P arty On P r emises / Inter nal

CC- B Y -S A 3.0 Sam Johnston by Cloud Computing T ypes

Cloud computing types

6.1 Private cloud

Private cloud is cloud infrastructure operated solely for asingle organization, whether managed internally or by athird-party, and hosted either internally or externally.[3]Undertaking a private cloud project requires a significantlevel and degree of engagement to virtualize the businessenvironment, and requires the organization to reevaluatedecisions about existing resources. When done right, itcan improve business, but every step in the project raisessecurity issues that must be addressed to prevent seri-ous vulnerabilities. Self-run data centers[68] are generallycapital intensive. They have a significant physical foot-print, requiring allocations of space, hardware, and en-vironmental controls. These assets have to be refreshedperiodically, resulting in additional capital expenditures.They have attracted criticism because users “still have tobuy, build, and manage them” and thus do not benefitfrom less hands-onmanagement,[69] essentially "[lacking]the economic model that makes cloud computing such anintriguing concept”.[70][71]

6.2 Public cloud

A cloud is called a “public cloud” when the services arerendered over a network that is open for public use. Pub-lic cloud services may be free.[72] Technically there maybe little or no difference between public and private cloudarchitecture, however, security consideration may be sub-stantially different for services (applications, storage, andother resources) that are made available by a serviceprovider for a public audience and when communicationis effected over a non-trusted network. Generally, publiccloud service providers like AmazonAWS,Microsoft andGoogle own and operate the infrastructure at their datacenter and access is generally via the Internet. AWS andMicrosoft also offer direct connect services called “AWSDirect Connect” and “Azure ExpressRoute” respectively,such connections require customers to purchase or lease aprivate connection to a peering point offered by the cloudprovider.[35]

6.3 Hybrid cloud

Hybrid cloud is a composition of two or more clouds (pri-vate, community or public) that remain distinct entitiesbut are bound together, offering the benefits of multipledeployment models. Hybrid cloud can also mean the abil-ity to connect collocation, managed and/or dedicated ser-vices with cloud resources.[3]

Gartner, Inc. defines a hybrid cloud service as a cloudcomputing service that is composed of some combina-tion of private, public and community cloud services,from different service providers.[73] A hybrid cloud ser-vice crosses isolation and provider boundaries so that itcan't be simply put in one category of private, public, orcommunity cloud service. It allows one to extend eitherthe capacity or the capability of a cloud service, by aggre-gation, integration or customization with another cloudservice.Varied use cases for hybrid cloud composition exist. Forexample, an organization may store sensitive client datain house on a private cloud application, but interconnectthat application to a business intelligence application pro-vided on a public cloud as a software service.[74] Thisexample of hybrid cloud extends the capabilities of theenterprise to deliver a specific business service throughthe addition of externally available public cloud services.Hybrid cloud adoption depends on a number of factorssuch as data security and compliance requirements, levelof control needed over data, and the applications an or-ganization uses.[75]

Another example of hybrid cloud is one where IT orga-nizations use public cloud computing resources to meettemporary capacity needs that can not be met by the pri-vate cloud.[76] This capability enables hybrid clouds toemploy cloud bursting for scaling across clouds.[3] Cloudbursting is an application deployment model in which an

7

application runs in a private cloud or data center and“bursts” to a public cloud when the demand for comput-ing capacity increases. A primary advantage of cloudbursting and a hybrid cloud model is that an organiza-tion only pays for extra compute resources when they areneeded.[77] Cloud bursting enables data centers to cre-ate an in-house IT infrastructure that supports averageworkloads, and use cloud resources from public or pri-vate clouds, during spikes in processing demands.[78]

The specialized model of hybrid cloud, which is builtatop heterogeneous hardware, is called “Cross-platformHybrid Cloud”. A cross-platform hybrid cloud is usu-ally powered by different CPU architectures, for exam-ple, x86-64 and ARM, underneath. Users can trans-parently deploy applications without knowledge of thecloud’s hardware diversity.[79] This kind of cloud emergesfrom the raise of ARM-based system-on-chip for server-class computing.

6.4 Others

6.4.1 Community cloud

Community cloud shares infrastructure between sev-eral organizations from a specific community with com-mon concerns (security, compliance, jurisdiction, etc.),whether managed internally or by a third-party, and ei-ther hosted internally or externally. The costs are spreadover fewer users than a public cloud (but more than a pri-vate cloud), so only some of the cost savings potential ofcloud computing are realized.[3]

6.4.2 Distributed cloud

Acloud computing platform can be assembled from a dis-tributed set of machines in different locations, connectedto a single network or hub service. It is possible to dis-tinguish between two types of distributed clouds: public-resource computing and volunteer cloud.

• Public-resource computing: This type of dis-tributed cloud results from an expansive defini-tion of cloud computing, because they are moreakin to distributed computing than cloud comput-ing. Nonetheless, it is considered a sub-class ofcloud computing, and some examples include dis-tributed computing platforms such as BOINC andFolding@Home.

• Volunteer cloud: Volunteer cloud computing ischaracterized as the intersection of public-resourcecomputing and cloud computing, where a cloudcomputing infrastructure is built using volunteeredresources. Many challenges arise from this type ofinfrastructure, because of the volatility of the re-sources used to built it and the dynamic environ-ment it operates in. It can also be called peer-

to-peer clouds, or ad-hoc clouds. An interest-ing effort in such direction is Cloud@Home, itaims to implement a cloud computing infrastructureusing volunteered resources providing a business-model to incentivize contributions through financialrestitution[80]

6.4.3 Intercloud

Main article: Intercloud

The Intercloud[81] is an interconnected global “cloud ofclouds”[82][83] and an extension of the Internet “networkof networks” on which it is based. The focus is on directinteroperability between public cloud service providers,more so than between providers and consumers (as is thecase for hybrid- and multi-cloud).[84][85][86]

6.4.4 Multicloud

Main article: Multicloud

Multicloud is the use of multiple cloud computing ser-vices in a single heterogeneous architecture to reducereliance on single vendors, increase flexibility throughchoice, mitigate against disasters, etc. It differs fromhybrid cloud in that it refers to multiple cloud services,rather than multiple deployment modes (public, private,legacy).[87][88]

7 Architecture

Cloud Storage(eg Database)

Cloud Platform

(eg Web Frontend)

Cloud Service(eg Queue)

Cloud Infrastructure

(eg Billing VMs)

Cloud computing sample architecture

Cloud architecture,[89] the systems architecture of thesoftware systems involved in the delivery of cloud com-puting, typically involves multiple cloud componentscommunicating with each other over a loose couplingmechanism such as a messaging queue. Elastic provisionimplies intelligence in the use of tight or loose couplingas applied to mechanisms such as these and others.

8 10 SEE ALSO

7.1 Cloud engineering

Cloud engineering is the application of engineering dis-ciplines to cloud computing. It brings a systematic ap-proach to the high-level concerns of commercialization,standardization, and governance in conceiving, develop-ing, operating and maintaining cloud computing systems.It is a multidisciplinary method encompassing contribu-tions from diverse areas such as systems, software, web,performance, information, security, platform, risk, andquality engineering.

8 Security and privacy

Main article: Cloud computing issues

Cloud computing poses privacy concerns because the ser-vice provider can access the data that is on the cloud at anytime. It could accidentally or deliberately alter or evendelete information.[90]Many cloud providers can share in-formation with third parties if necessary for purposes oflaw and order evenwithout a warrant. That is permitted intheir privacy policies which users have to agree to beforethey start using cloud services.[91] Solutions to privacy in-clude policy and legislation as well as end users’ choicesfor how data is stored.[90] Users can encrypt data that isprocessed or stored within the cloud to prevent unautho-rized access.[2][90]

According to the Cloud Security Alliance, the top threethreats in the cloud are “Insecure Interfaces and API’s”,“Data Loss & Leakage”, and “Hardware Failure” whichaccounted for 29%, 25% and 10% of all cloud securityoutages respectively — together these form shared tech-nology vulnerabilities. In a cloud provider platform be-ing shared by different users there may be a possibil-ity that information belonging to different customers re-sides on same data server. Therefore, Information leak-age may arise by mistake when information for one cus-tomer is given to other.[92] Additionally, Eugene Schultz,chief technology officer at Emagined Security, said thathackers are spending substantial time and effort lookingfor ways to penetrate the cloud. “There are some realAchilles’ heels in the cloud infrastructure that are mak-ing big holes for the bad guys to get into”. Because datafrom hundreds or thousands of companies can be storedon large cloud servers, hackers can theoretically gain con-trol of huge stores of information through a single attack— a process he called “hyperjacking”.There is the problem of legal ownership of the data (If auser stores some data in the cloud, can the cloud providerprofit from it?). Many Terms of Service agreements aresilent on the question of ownership.[93]

Physical control of the computer equipment (privatecloud) is more secure than having the equipment off siteand under someone else’s control (public cloud). This de-

livers great incentive to public cloud computing serviceproviders to prioritize building and maintaining strongmanagement of secure services.[94] Some small busi-nesses that don't have expertise in IT security could findthat it’s more secure for them to use a public cloud.There is the risk that end users don't understand the is-sues involved when signing on to a cloud service (personssometimes don't read the many pages of the terms of ser-vice agreement, and just click “Accept” without reading).This is important now that cloud computing is becomingpopular and required for some services to work, for ex-ample for an intelligent personal assistant (Apple’s Siri orGoogle Now).Fundamentally private cloud is seen as more secure withhigher levels of control for the owner, however publiccloud is seen to be more flexible and requires less timeand money investment from the user.[95]

9 The future

According to Gartners Hype cycle, cloud computing hasreached a maturity that leads it into a productive phase.This means that most of the main issues with cloud com-puting have been addressed to a degree that clouds havebecome interesting for full commercial exploitation. Thishowever does not mean that all the problems listed abovehave actually been solved, only that the according riskscan be tolerated to a certain degree.[96] Cloud comput-ing is therefore still as much a research topic, as it is amarket offering.[97] What is clear through the evolutionof Cloud Computing services is that the CTO is a ma-jor driving force behind Cloud adoption.[98] The majorCloud technology developers continue to invest billions ayear in Cloud R&D; for example, in 2011Microsoft com-mitted 90% of its $9.6bn R&D budget to Cloud.[99] Ad-ditionally, more industries are turning to cloud technol-ogy as an efficient way to improve quality services due toits capabilities to reduce overhead costs, downtime, andautomate infrastructure deployment.[100]

10 See also• Category:Cloud computing providers

• Category:Cloud platforms

• Cloud computing comparison

• Cloud management

• Cloud research

• Cloud storage

• Edge computing

• Fog computing

9

• Grid computing

• eScience

• iCloud

• Mobile cloud computing

• Personal cloud

• Robot as a Service

• Service-Oriented Architecture

• Synaptop

• Ubiquitous computing

• Web computing

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12 External links• Evolution of as-a-Service Era in Cloud. A reviewon as-a-Service Framework (White paper by Dr.Sugam Sharma), 2015.

• Above the clouds: a Berkeley view of cloud com-puting, technical report no. UCB/EECS-2009-28,Feb 10, 2009, http://www.eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-28.html

12 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

13 Text and image sources, contributors, and licenses

13.1 Text• Cloud computing Source: https://en.wikipedia.org/wiki/Cloud_computing?oldid=682564018 Contributors: Zundark, William Avery,ChangChienFu, Heron, Jose Icaza, Jdlh, Michael Hardy, Mahjongg, Rw2, Haakon, Ronz, Julesd, Andrewman327, DJ Clayworth, Tp-bradbury, Furrykef, Saltine, Fvw, Dbabbitt, Tkdcoach, Rossumcapek, Chealer, PBS, Lapax, Rursus, SC, Jleedev, Mattflaschen, To-bias Bergemann, Lysy, Martinwguy, Giftlite, Metapsyche, Smjg, Graeme Bartlett, Ryanrs, HangingCurve, Mckaysalisbury, DavidLam,Utcursch, SoWhy, Pgan002, SarekOfVulcan, Beland, Bumm13, Sfoskett, Xinconnu, Axelangeli, Now3d, ShortBus, Chem1, Thorwald,Mike Rosoft, Slady, Discospinster, Rich Farmbrough, Hydrox, YUL89YYZ, Bender235, ESkog, Neko-chan, Syp, Shanes, Jpgordon, Shax,Sanjiv swarup, Richi, CKlunck, Justinc, Mdd, Alansohn, Gary, Csabo, Richard Harvey, Tobych, Free Bear, Kessler, Diego Moya, Andrew-pmk, Ricky81682, Ashley Pomeroy, Snowolf, Wtmitchell, Velella, Wtshymanski, Stephan Leeds, RubenSchade, LFaraone, Versageek,Blaxthos, Duplode, Richwales, Walshga, Oleg Alexandrov, Skrewler, Stuartyeates, Brianwc, Lordfaust, Firsfron, Woohookitty, Mind-matrix, RHaworth, TheNightFly, Ruud Koot, WadeSimMiser, Trödel, Cbdorsett, GregorB, Dogsbody, SPACEBAR, Littlewild, Man-darax, RichardWeiss, BD2412, Pmj, Tlroche, Jorunn, Rjwilmsi, Nightscream, Wooptoo, Salix alba, MZMcBride, Vegaswikian, Bodhran,ElKevbo, Bubba73, The wub, Syced, FayssalF, Makru, Windchaser, Jmc, Nogburt, Crazycomputers, Jacob1044, A.K.Karthikeyan, Intgr,David H Braun (1964), Ahunt, Imnotminkus, Chobot, DVdm, Guliolopez, Bgwhite, Wavelength, RussBot, Bhny, Stephenb, Manop,SteveLoughran, Rsrikanth05, Bovineone, Tungsten, SamJohnston, LandoSr, Gram123, NawlinWiki, Dialectric, Grafen, Welsh, Hogne,Akropp, Dethomas, PhilipC, Moe Epsilon, Tony1, Jerome Kelly, Wizzard, Jeh, Sarathc, Bikeborg, Yonidebest, Rolf-Peter Wille, Zzu-uzz, Sissyneck, Timwayne, E Wing, Juliano, JLaTondre, DoriSmith, Allens, Katieh5584, Snaxe920, Otto ter Haar, Bernd in Japan, Li-ujiang, Tom Morris, Victor falk, Goetz, Kimdino, DanStern~enwiki, Luk, Mgaffney, Palapa, SmackBot, Ashley thomas80, JoshDuff-Man, McGeddon, Gigs, PhilJackson, CastAStone, C.Fred, Elminster Aumar, Davewild, WookieInHeat, Jab843, AnOddName, Lainagier,Yamaguchi , Gilliam, Ohnoitsjamie, Skizzik, Samveen, Kawana, Rmosler2100, Chris the speller, Bidgee, Ebhakt, Thumperward,Wilsonodk, Siddii~enwiki, RayAYang, Deli nk, Jerome Charles Potts, Dlohcierekim’s sock, Letdorf, Nbarth, Colonies Chris, A. B.,John Reaves, Scwlong, Wynand.winterbach, Nabeez, Mike hayes, Tped, Frap, StefanB sv, Jacob Poon, OSborn, Uozef, Billytkid, GV-nayR, LuchoX, Abrahami, Speedplane, Valenciano, Preetesh.rao, Dreadstar, Drphilharmonic, DMacks, Shswanson, Vina-iwbot~enwiki,Bejnar, Vasiliy Faronov, Spiritia, KenCavallon, Acrooney, ArglebargleIV, AbdullahHaydar, Harryboyles, Gandalf44, JzG, Kuru, Oskil-ian, Tomhubbard, Gobonobo, Darktemplar, Robofish, JoshuaZ, Kashmiri, Minna Sora no Shita, IronGargoyle, Ckatz, Kompere, Beet-stra, Mr Stephen, Ehheh, Larrymcp, Optakeover, Waggers, TastyPoutine, Dr.K., Kvng, Belfry, Keahapana, Hu12, Meitar, Quaeler,Spo0nman, Jonasalmeida, IvanLanin, UncleDouggie, Rnb, Mjboniface, Majora4, Courcelles, Dlohcierekim, Chris55, Patrickwooldridge,FatalError, JForget, VoxLuna, Ourhistory153, Randhirreddy, Earthlyreason, Eric, JohnCD, Bill.albing, Kmsmgill, NaBUru38, Flood6,Sanspeur, WeisheitSuchen, Alexamies, Myasuda, Metatinara, Jehfes, Rotiro, Yaris678, Cydebot, Mblumber, MC10, UncleBubba, An-thonyhcole, GRevolution824, Dancter, Clovis Sangrail, Christian75, Ameliorate!, Kozuch, Neustradamus, Casliber, Malleus Fatuorum,Thijs!bot, Epbr123, Kubanczyk, Dschrader, Wikid77, Vicweast, Shoaibnz, Ugarit, Vondruska, Vertium, John254, James086, Edchi, Ed-Johnston, Nick Number, Bob.gourley@comcast.net, Heroeswithmetaphors, Tree Hugger, Dawnseeker2000, Escarbot, Porqin, MrMar-mite, Seaphoto, Shirt58, Marokwitz, Smartse, Dinferno, Silver seren, MrKG, Lbecque, DaudSharif, Tangurena, Dougher, Barek, MER-C, Dsp13, The Transhumanist, Jldupont~enwiki, MB1972, Mwarren us, Rms77, Ispabierto, Greensburger, East718, Ny156uk, Spojrze-nie, Magioladitis, Swikid, Bongwarrior, Lmbhull, JamesBWatson, Mathematrucker, GaryGo, Steven Walling, Cic, ForthOK, Jeffsnox,Hamiltonstone, Be-nice:-), Pleft, Kibbled bits, Cpl Syx, Balaarjunan, SBunce, JaGa, Kgfleischmann, Philg88, Bufh, Pikolas, Zevnik,Curtbeckmann, Pisapatis, Dezrtluver, CliffC, Iamthenewno2, Casieg, CitizenB, Parveson, Jack007, Xiler, Bus stop, Vermtt, Miguelcal-das, Alankc, Mariolina, Linuxbabu~enwiki, JonathonReinhart, Tgeairn, J.delanoy, PCock, Trusilver, Anandcv, Vpfaiz, Uncle Dick, Mau-rice Carbonaro, Jesant13, Ginsengbomb, Mathglot, Jarrad Lewis, Tsmitty31, Betswiki, Tonyshan, Staceyeschneider, NewEnglandYankee,Quantling, BostonRed, Biglovinb, Olegwiki, Bshende, KylieTastic, Raspalchima, HenryLarsen, Paulmmn, Songjin, Bonadea, Pegordon,Swolfsg, Idioma-bot, Laurenced, Martin.ashcroft, Imtiyazali4all, Bobwhitten, Obdurodon, Huygens 25, Vranak, 28bytes, VolkovBot, JeffG., Dogbertwp, Edeskonline, Bkengland, Priyo123, FatUglyJo, Nyllo, Philip Trueman, A.Ward, Zarcusian, TXiKiBoT, Itangalo, Vipin-hari, Technopat, Guillaume2303, Anonymous Dissident, Danielchalef, Markus95, Markfetherolf, GcSwRhIc, Monkey Bounce, Piperh,Rich Janis, Felipebm, Martin451, Broadbot, Willit63, Amog, Figureskatingfan, Everything counts, SpecMode, Johnpltsui, Andy Din-gley, Finngall, Haseo9999, Lamro, Garima.rai30, The Seventh Taylor, Falcon8765, VanishedUserABC, Nelliejellynoonaa, Sapenov, Lit-tleBenW, Jimmi Hugh, Logan, OsamaK, Biscuittin, SieBot, Skyrail, Moonriddengirl, EwokiWiki, Doctorfree, Sakaal, Dawn Bard, TimothyCooper, Navywings, Yintan, SuzanneIAM, Kpalsson, Jerryobject, Fishtron, Keilana, Chmyr, Heyitscory, Bentogoa, Happysailor, Flyer22,Jojalozzo, Nopetro, Snideology, Yerpo, Reservoirhill, OsamaBinLogin, Dominik92, Xe7al, North wiki, Techman224, Vykk, Rosiestep,Fuddle, StaticGull, Classivertsen, Bijoysr, WikiLaurent, Superbeecat, Laser813, Shinerunner, Denisarona, Motyka, Dlrohrer2003, Mar-tarius, Simonmartin74, Elassint, ClueBot, GorillaWarfare, Wasami007, The Thing That Should Not Be, Cdhkmmaes, Nnemo, Czarkoff,Axorc, Jasapir, Drmies, VQuakr, Mild Bill Hiccup, Myokobill, Allenmwnc, Enc1234, LizardJr8, Bob bobato, Darren uk, Esthon~enwiki,Auntof6, 718 Bot, Pointillist, Jonathan.robie, Loadbang, Stuart.clayton.22, Ktr101, Excirial, Pumpmeup, Alexbot, Jusdafax, Sajeer50,Hfoxwell, Eeekster, Nasonmedia, Muhandes, SunnySideOfStreet, Technobadger, 842U, Cmartell, M.O.X, Razorflame, Jinlye, Schreiber-Bike, Five-toed-sloth, Craig.Coward, Hasbrook, Jakemoilanen, Vdmeraj, PCHS-NJROTC, Johnuniq, Vigilius, DumZiBoT, Jack Bauer00,Steveozone, Darkicebot, Beltman R., Lorddunvegan, XLinkBot, AgnosticPreachersKid, Roxy the dog, Njkool, Stickee, Sponsion, Feinoha,Chanakal, Bpgriner, C. A. Russell, Avoided, Fergus Cloughley, Imllorente, Skarebo, WikHead, Galzigler, Mifter, Badgernet, PcCof-fee, Jbeans, Eleven even, Jht4060, NonNobisSolum, Richard.McGuire88, Sandipk singh, RealWorldExperience, Y2l2, Edepa, B Fizz,Dbrisinda, Deineka, Bazj, Addbot, American Eagle, TimFreeman701, Ramu50, Mortense, Grayfell, Realtimer77, Sean R Fox, Mabdul,IXavier, VijayKrishnaPV, Fcalculators, Mkdonqui, Amore proprio, Tanhabot, Barmijo, TutterMouse, Fieldday-sunday, Scientus, Shakeel-rashed, CanadianLinuxUser, Ethoslight, Kristiewells, Cst17, Mohamed Magdy, MrOllie, Download, Robert.Harker, Hatfields, Glane23,Mhodapp, Glass Sword, JimDelRossi, Favonian, Optatus, Stbrodie1, Terrillja, Numbo3-bot, Superkillball, Cybercool10, HandThatFeeds,Ashleymcneff, Tide rolls, שי ,דוד Krano, NeD80, Hunyadym, Luckas Blade, Teles, Cloudcoder, Jarble, Mlavannis, Shri ram r, Hercule-Bot, Enaiburg, Gamber34, Legobot, Avlnet, Jerichochang97, Luckas-bot, BaldPark, ZX81, Yobot, Evagarfer~enwiki, Themfromspace,Dfxdeimos, Legobot II, Librsh, Jamalystic, Bruce404, Asieo, Indigokk, Reshadipoor, Washburnmav, Identity20, Adam Hauner, Ime-son, Javaeu, Thesurfpup, Achimew, Lerichard, Knoxi171, ByM4k5, Tiburondude, Aburreson, Jean.julius, Sweerek, Peter Flass, Sql er2,WikiScrubber, Sivanesh, IANYL, Deicool, AnomieBOT, Momoricks, DemocraticLuntz, Dmichaud, Pgj1997, 1exec1, Cronos4d, Thad-deusB, Jim1138, IHSscj, JackieBot, Iamdavinci, CloudComputing, Yaraman, Mbblake, AdityaTandon, Csigabi, Felixchu, Materialsci-entist, RobertEves92, JamesLWilliams2010, The High Fin Sperm Whale, Citation bot, Jkelleyy, OllieFury, Shan.rajad23, ArthurBot,Quebec99, YoungManBlues, NW’s Public Sock, PavelSolin, LemonairePaides, Mwmaxey, Xqbot, L200817s, Alexlange, Lairdp, Avneral-gom, Capricorn42, Rakesh india, Surajpandey10, Pontificalibus, Nfr-Maat, Nasnema, Poliverach, Gkorland, Ohspite, Ramnathkc, Wlouth,

13.1 Text 13

Tatatemc, Chadastrophic, Dbake, NFD9001, Emrekenci, Anna Frodesiak, Explorer09, BrianWren, Peterduffell, Macholl, Anamika.search,EricTheRed20, Michael.owen4, MarkCPhinn, NocturneNoir, Miym, J04n, GrouchoBot, Onmytoes4eva, Frosted14, ChristopherKing-Chemist, ProtectionTaggingBot, Rsiddharth, Omnipaedista, Andyg511, DarrenOP, RibotBOT, Mattg82, TonyHagale, Jbekuykendall,Jwt1801, Mathonius, Amaury, Yodaspirine, Vmops, WootFTW, WithWhich, Liyf, Mobilecloud, Figaronline, BrennaElise, Shadow-jams, E0steven, Chaheel Riens, Jef4444, Person1988, A.amitkumar, Dan6hell66, RetiredWikipedian789, Mmanie, FrescoBot, Imtiyaz81, Adlawlor, Yuchan0803, Zachnh, Manusnake, Blackguard SF, Cajetan da kid, Paj mccarthy, Ronen.hamias, Mark Renier, CloudBot,Lonaowna, Sariman~enwiki, Jakeburns99, Jesse.gibbs.elastra, W Nowicki, Estahl, Pottersson, Freddymay, Recognizance, Nakakapag-pabagabag, MichealH, Gratridge, Ashakeri3596, Ummelgroup, Sebastiangarth, HJ Mitchell, Pete maloney, Scott A Herbert, Zhanghaisu,Berny68, Wireless Keyboard, HamburgerRadio, Yinchunxiang, Lmp90, Rickyphyllis, Acandus, Vasq0123, Winterst, Monkeyfunforid-iots, Pinethicket, I dream of horses, Elockid, HRoestBot, Samuraiguy, Jonesey95, Eddiev11, AcuteSys, MJ94, PMstdnt, JLRedperson,Li Yue Depaul, Tinton5, Skyerise, Ggafraser, A8UDI, Dannymjohnson, Nimbus prof, RedBot, Janniscui, Manishekhawat, Bigfella1123,SpaceFlight89, Aneesh1981, Troy.frericks, Σ, Natishalom, Agemoi, Piandcompany, Noisalt, Cloudnitc, Jandalhandler, Devinek22, Undis-covered778, No1can, Ras67, Maasmiley, Abligh, Reconsider the static, AstralWiki, Juliashapiro, SW3 5DL, Niri.M, Msileinad, Hughesjp,Skovigo, Kjohnthomas, Jburns2009, JanaGanesan, ConcernedVancouverite, Trappist the monk, Declan Clam, Iminvinciblekris, SchreyP,Rajeshkamboj, Avermapub, KotetsuKat, Sanmurugesan, Markus tauber, Burrows01, Lotje, Kieransimkin, EDC5370, Dinamik-bot, Vre-nator, Danielrs, LilyKitty, Richramos, Clarkcj12, Robscheele, SeoMac, Miracle Pen, Çalıştay, Ansumang, Ycagen, Aoidh, Eco30, ReaperEternal, Crysb, Whitehouseseo, Info20072009, Jeffrd10, Pmell, Imnz730, Cemgurkok, Suffusion of Yellow, Taicl13, Tbhotch, Latha as,Colleenhaskett, Balvord, Hutch8700, MarshallWilensky, Nesjo, DARTH SIDIOUS 2, OmbudsTech, MidgleyC, Mean as custard, Sumdeus,RjwilmsiBot, Veerapatr.k, TjBot, DexDor, Alph Bot, Tdp610, Jon.ssss, Nasserjune, Amartya71, VernoWhitney, Darkyeffectt, Chriswrit-ing, Vpolavia, Beleg Tâl, Ianmolynz, DuineSidhe, DSP-user, Learn2009, Aurifier, Jineshvaria, Pmorinreliablenh, Rollins83, Bamtelim,Adjectivore, Lipun4u, R39132, Nookncranny, J36miles, EmausBot, Editorfry, Understated1, Acather96, Pjposullivan, Deepalja, Wik-itanvirBot, Gozzilli, Rutger72, PaulQSalisbury, Logical Cowboy, Timtempleton, Eusbls, DragonflyReloaded, Macecanuck, Ajraddatz,Heracles31, Noloader, Jbadger88, Dewritech, Clutterpad, Ianlovesgolf, Gmm24, GoingBatty, RA0808, Snydeq, AoV2, Vanished userzq46pw21, Tisane, Sp33dyphil, Fzk chc, Luigi Baldassari, Solarra, Njcaus, Moswento, Sam Tomato, Wikipelli, 623des, K6ka, Tmguru,AsceticRose, Srastogis, Anirudh Emani, Zafar142003, Thecheesykid, Francis.w.usher, Hardduck, Vishwaraj.anand00, QuentinUK, Man-asprakash79, Jtschoonhoven, BobGourley, Bongoramsey, Fæ, Josve05a, DeleoB, Ppachwadkar, Stevenro, Aaditya025, Trinidade, Wack-ywace, 9Engine, TunaFreeDolfin, Tom6, Kronostar, Wtsao, Aavindraa, A930913, GZ-Bot, H3llBot, Chintan4u, Eniagrom, Amanisdude,Kyerussell, Machilde, Mr little irish, Tolly4bolly, Jay-Sebastos, Thexman20, Coasterlover1994, Scott.somohano, L Kensington, Ready,Mayur, Aflagg99, Donner60, Skumarvimal, Zfish118, MillinKilli, Puffin, Ego White Tray, Orange Suede Sofa, Rangoon11, Bill williamcompton, MainFrame, JohnnyJohnny, StartupMonkey, ClamDip, Kenny Strawn, MaxedoutnjNJITWILL, Alex5678, Msfitzgibbonsaz, Sha-julin, Nurnware, EmilyEgnyte, DASHBotAV, NatterJames, Jhodge88, JohnJamesWIlson, 28bot, JonRichfield, Frozen Wind, Petrb, RS-HKG, Dyepoy05, ClueBot NG, Sharktopus, Horoporo, Michaelmas1957, DellTechWebGuy, JackGreenmaven, Slwri, VicoSystems1, Busi-nesstecho, DrFurey, Dadomusic, Cloudcto, Amoebat, MelbourneStar, This lousy T-shirt, Catlemur, Qarakesek, CPieras, Satellizer, A520,Markqu, Bulldog73, Kkh03, Ethicalhackerin2010, Bped1985, Stickyboi, Candace Gillhoolley, Happyinmaine, Leifnsn, Hemapi, LordRoem, Gxela, Nikoschance, The Master of Mayhem, Shawnconaway, Einasmadi, Qusayfadhel, Certitude1, Tylerskf, PJH4-NJITWILL,IDrivebackup, Lionheartf, O.Koslowski, Kevin Gorman, Dimos2k, ScottSteiner, Helotrydotorg, Alanmonteith, Digestor81, Widr, Scot-tonsocks, WikiPuppies, Gawali.jitesh, Andersoniooi, Rebuker, Chuahcsy, Carl presscott, Qoncept, Keynoteworld, Fearlessafraid, Jo-hananl, Helpful Pixie Bot, OAnimosity, Leoinspace, Iste Praetor, HMSSolent, Tastic007, Titodutta, Calabe1992, DBigXray, Lavanyalava,Aditya.smn, Whitehatpeople, Elauminri, Angrywikiuser, BG19bot, RLSnow, SocialRadiusOly, MikeGeldens, Oluropo, Krenair, Cloudx-tech, Sfiteditor, ValStepanova, Joerajeev, Robert.ohaver, Cornelius383, Dpsd 02011, Jimsimwiki, Markoo3, Rijinatwiki, Bhargavee, Soft-devusa, Northamerica1000, Nadeemamin, Jayvd, San2011, Shaysom09, Lee.kinser, GhostModern, Om23, Panoramak, Avillaba, HallowsAG, Wiki13, Stevevictor134, MusikAnimal, Frze, Er.madnet, BDavis27, TylerFarell, Itzkishor, Mark Arsten, Compfreak7, Kirananils,EEldridge1, Leinsterboy, Dmcelroy1, Philopappos86, ThomasTrappler, StrategicBlue, Joydeep, Anne.naimoli, Jbucket, JMJeditor, Blvrao,Mychalmccabe, JDC321, Watal, Latticelattuce, Wretman, Frdfm, Phil.gagner, Elasticprovisioner, DPL bot, Andromani, Tramen12, Tor-turedgenius, Phazoni, Chapmagr, Jmillerfamily, TJK4114, Subbumv, Dinhthaihoang, Charvoworld, Mpcirba, Smileyranger, Klilidiplomus,Ssabihahmed, Achowat, Wannabemodel, ChambersDon, Fylbecatulous, BrianWo, Knodir, EricEnfermero, JoeBulsak, BattyBot, 21hat-tongardens, Eduardofeld, Kridjsss, Dlowenberger, 1337H4XX0R, Kunitakako, Elbarcino, ChannelFan, Haroldpolo, Cloudfest, Teammm,Xena77, Anhtrobote, Pratyya Ghosh, Tuwa, Mdann52, D rousslan, MPSTOR, Pea.hamilton, Crackerspeanut12, Mrt3366, Cloudreviewer,ChrisGualtieri, LarryEFast, Jackoboss, Valentina Ochoa, Battling McGook, Beanilkumar, Mediran, EliyahuStern, Beer2beer, EuroCarGT,Prodirus, Fb2ts, SimonBramfitt, Xxyt65r, Mheikkurinen, Nithdaleman, Jags707, EagerToddler39, Davidogm, Padmaja cool, Zingophali-tis, Zeeyanwiki, Mcsantacaterina, Shierro, Weternuni, Webclient101, Raushan Shahi, Sjames1, Mogism, Gotocloud, Derekvicente, No-zomimous, Anderson, Cerabot~enwiki, Chishtigharana, Lone boatman, Fabrice Florin (WMF), PonmagalMalar, Naturelover007, TwoT-woHello, Thewebartists013, TechyOne, Aloak1, Vikas gupta70, Arnavrox, Frosty, SFK2, Hair, MartinMichlmayr, Sk8trboi199, Os con-nect, Jamesx12345, Shubhi choudhary, Joe1689, Sriharsh1234, Viralshah0704, Millycylan, Lorenrb, Kevin12xd, Choor monster, Dr-joseph7, BurritoBazooka, OSRules, Phamnhatkhanh, Waynej6, Avacam, Khan.sharique1994, Amitgupta2792, Zimzaman, Faizan, Chiefs-partan, Epicgenius, Shivalikisam, FallingGravity, Ruinjames, Ramanrawal, Acaliguiran, Vanamonde93, S.sameermanas, JaredRClemence,I am One of Many, John-readyspace, Whitecanvas, Jlamus, Manishrai tester, FunkyMonk101, Carrot Lord, Jp4gs, Melonkelon, MangaiVellingiri, Lena322, Craig developer, Danieljohnc, Alfy32, Solomon35, Rkocher, 5c0tt-noe, Thinkcd, Lsteinb, Tentinator, Marinac93, Aa-ronito, Evano1van, Kapils1255, Olynickjeff, Marcio10Luiz, EvergreenFir, Cookingwithrye, Jopgro, Fsandlinux, Backendgaming, Frmarz,5andrew1, Nextlevelwb, Maura Driscoll, Flat Out, Halkemp, Couth, Dreamfigure, Murus, Saqibazmat, Jugaste, Babitaarora, Bloonstd-fan360, Comp.arch, Kewi69, Metadox, Jbrucb, Podger.the, Henhuawang, Katepressed, Tbilisi2013, Asarada, Rzicari, AcidBlob, Rodie151,Fatdan786, NottNott, Dwils098, Max1685, Mariatim, Ginsuloft, ArmitageAmy, Didi.hristova, IMMS, Insomniac14, Corey Rose, Aca-lycine, Jackmcbarn, Dudewhereismybike, PracticalScrum, TDBA, Bob Staggert, Rkanojia, Pcpded, Jora8488, Deeepak1300, Harshac89,Goofette, WikiJuggernaut, Gracecheung08, Cloud guru28, Lucy1982, CloudBurster, PierreCoyne, Sweetsadamali, LookToLuke, Justuj,Mareep, Wlwells67833, JaconaFrere, Theworm4321, JenniferAndy, Lakun.patra, Skr15081997, Rax sa, Ssgmu55, Nclemen2, 7Sidz, SofiaLucifairy, Abhinavgupta007, Sfroberts, Musabhai2, Mgt88drcr, Ajabak, Edwardsmith285, Nyashinski, MtthwAndrn, Shanhuyang, Nas-saraf, Amenychtas, Uk1211, Deepika Sreerama, Monkbot, Cjbwin, Allanamiller, Sylvesta101, Lucyloo10, Kalpesh radadiya, Dansullivan-pdx, Honyczek, Bingoarunprasath, BethNaught, Security.successfactors, Jblews, Mboxell, Mannanseo, MorePix, ThatWriterBloke, Ipsrso-lutions, JoelAaronSeely, Biblioworm, Science.Warrior, Daniel.moldovan, Schwarrrtz, Gk9999, Northbridge Secure, Twoosh, Cloudwizard,Thandi moyo, HMSLavender, Wrightandru, Ferozahmed0382, Mkchendil, Tonysmith2014, Manjaribalu, Ramvalleru, Daniela C DeMaria,Brandon Connor, Andy7809, Chicodoodoo, MONISHAGEORGE,MVMeena, KH-1, Garywfchan, Sahit1109, Tweeks-va, Ss.jarvisboyle,Cubexsweatherly, Nicky mathew, Stephenzhang.cs, Srinivas.dgm, Spiderjerky, Dtechinspiration, Amagi82, Lalith269, Headinthecloud,Shantan 1995, Kethrus, Edavinmccoy, Zellabox, Mj3ngr, Abcdudtc, Enkakad, Nei Wg Khang, Selvarajrajkanna, Shivanagakrishna, Fer-

14 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

vourPriyanka, Naveenwilder, Alexsmith22, Sanjeev.rawat86, Quarterbear, 95jenn, Yinongchen, Amit Seo Expert, Robbetto, Awm165,Supdiop, Nemesis2473, Peterju35, KasparBot, Dr.Rajan.Kumar.Yadav, Rucoseivas, Arjunkumaran, Aaditysony1, Adpindia, Johnny wiki2006, Btechf, Dawnpetworth5, BBpowers, GNoorPCtronics, Hermionegranger321, Asmbokliu, Salikgondal, Diana Marko, PaulDejean,Canaanb12, RansonBrown, Alenp21, Jashu1994, Kamcdonald and Anonymous: 2576

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