Cloud computing, Thinking Outside the Box
Cloud computing, Thinking Outside the Box
Cloud computing is Internet- (“cloud-”) based development and use of computer technology (“computing“). In concept, it is a paradigm shift whereby details are abstracted from the users who no longer need knowledge of, expertise in, or control over the technology infrastructure “in the cloud” that supports them. Cloud computing describes a new supplement, consumption and delivery model for IT services based on Internet, and it typically involves the provision of dynamically scalable and often virtualized resources as a service over the Internet.
The term cloud is used as a metaphor for the Internet, based on the cloud drawing used to depict the Internet in computer network diagrams as an abstraction of the underlying infrastructure it represents. Typical cloud computing providers deliver common business applications online which are accessed from a web browser, while the software and data are stored on servers.
These applications are broadly divided into the following categories: Software as a Service (SaaS), Utility Computing, Web Services, Platform as a Service (PaaS), Managed Service Providers (MSP), Service Commerce, and Internet Integration.
Cloud computing can be confused with:
- Grid computing — “a form of distributed computing, whereby a ‘super and virtual computer’ is composed of a cluster of networked, loosely coupled computers acting in concert to perform very large tasks”
- Utility computing — the “packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility, such as electricity“;
- Autonomic computing — “computer systems capable of self-management“.
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-computing offerings employ the utility computing model, which is analogous to how traditional utility services (such as electricity) are consumed, whereas others bill on a subscription basis. 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-effect of this approach is that overall computer usage rises dramatically, as customers do not have to engineer for peak load limits. In addition, “increased high-speed bandwidth” makes it possible to receive the same response times from centralized infrastructure at other sites.
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) or subscription (time-based, like a newspaper) basis with little or no upfront cost. Other benefits of this time sharing-style approach are low barriers to entry, shared infrastructure and costs, low management overhead, and immediate access to a broad range of applications. In general, users can terminate the contract at any time (thereby avoiding return on investment risk and uncertainty), and the services are often covered by service level agreements (SLAs) with financial penalties.
According to Nicholas Carr, the strategic importance of information technology is diminishing as it becomes standardized and less expensive. He argues that the cloud computing paradigm shift is similar to the displacement of electricity generators by electricity grids early in the 20th century.
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 where the 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 not make great fiscal sense. Other factors impacting the scale of any potential cost savings include the efficiency of a company’s data center as compared to the cloud vendor’s, the company’s existing operating costs, the level of adoption of cloud computing, and the type of functionality being hosted in the cloud.
The majority of cloud computing infrastructure, as of 2009[update], consists of reliable services delivered through data centers and built on servers. Clouds often appear as single points of access for all consumers’ computing needs. Commercial offerings are generally expected to meet quality of service (QoS) requirements of customers and typically offer SLAs.  Open standards are critical to the growth of cloud computing, and open source software has provided the foundation for many cloud computing implementations.
The Cloud is a term that borrows from telephony. Up to the 1990s, data circuits (including those that carried Internet traffic) were hard-wired between destinations. Then, long-haul telephone companies began offering Virtual Private Network (VPN) service for data communications. Telephone companies were able to offer VPN-based services with the same guaranteed bandwidth as fixed circuits at a lower cost because they could switch traffic to balance utilization as they saw fit, thus utilizing their overall network bandwidth more effectively. As a result of this arrangement, it was impossible to determine in advance precisely which paths the traffic would be routed over. The cloud symbol was used to denote that which was the responsibility of the provider, and cloud computing extends this to cover servers as well as the network infrastructure.
The underlying concept of cloud computing dates back to 1960, when John McCarthy opined that “computation may someday be organized as a public utility“; indeed it shares characteristics with service bureaus that date back to the 1960s. In 1997, the first academic definition was provided by Ramnath K. Chellappa who called it a computing paradigm where the boundaries of computing will be determined by economic rationale rather than technical limits. The term cloud had already come into commercial use in the early 1990s to refer to large Asynchronous Transfer Mode (ATM) networks.
Loudcloud, founded in 1999 by Marc Andreessen, was one of the first to attempt to commercialize cloud computing with an Infrastructure as a Service model. By the turn of the 21st century, the term “cloud computing” began to appear more widely, although most of the focus at that time was limited to SaaS, called “ASP’s” or Application Service Providers, under the terminology of the day.
In the early 2000s, Microsoft extended the concept of SaaS through the development of web services. IBM detailed these concepts in 2001 in the Autonomic Computing Manifesto, which described advanced automation techniques such as self-monitoring, self-healing, self-configuring, and self-optimizing in the management of complex IT systems with heterogeneous storage, servers, applications, networks, security mechanisms, and other system elements that can be virtualized across an enterprise.
Amazon played a key role in the development of cloud computing by modernizing their data centers after the dot-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 through Amazon Web Services on a utility computing basis in 2005. This characterization of the genesis of Amazon Web Services has been characterized as an extreme over-simplification by a technical contributor to the Amazon Web Services project.
In 2007, Google, IBM, and a number of universities embarked on a large scale cloud computing research project. 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”, 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 in significant reductions in other areas.”
In July 2008, HP, Intel Corporation and Yahoo! announced the creation of a global, multi-data center, open source test bed, called Open Cirrus , designed to encourage research into all aspects of cloud computing, service and datacenter management. Open Cirrus partners include the NSF, the University of Illinois (UIUC), Karlsruhe Institute of Technology, the Infocomm Development Authority (IDA) of Singapore, the Electronics and Telecommunications Research Institute (ETRI), the Malaysian Institute for Microelectronic Systems (MIMOS ), and the Institute for System Programming at the Russian Academy of Sciences (ISPRAS).
Despite efforts (such as US-EU Safe Harbor) to harmonize the legal environment, as of 2009[update], providers such as Amazon cater to major markets (typically the United States and the European Union) by deploying local infrastructure and allowing customers to select “availability zones.” Nonetheless, concerns persist about security and privacy from individual through governmental levels (e.g., the USA PATRIOT Act, the use of national security letters, and the Electronic Communications Privacy Act‘s Stored Communications Act). More risks are mentioned in Seven Technical Security Myths of the Cloud
On January 13, 2010, HP and Microsoft announced  an agreement to invest $250 million over the next three years to significantly simplify technology environments via cloud computing. The two companies will collaborate on an engineering roadmap for converged application platforms, comprehensive virtualization solutions and integrated management offerings to advance cloud computing.
 Legal issues
In March 2007, Dell applied to trademark the term “cloud computing” (U.S. Trademark 77,139,082) in the United States. The “Notice of Allowance” the company received in July 2008 was cancelled in August, resulting in a formal rejection of the trademark application less than a week later.
In November 2007, the Free Software Foundation released the Affero General Public License, a version of GPLv3 intended to close a perceived legal loophole associated with free software designed to be run over a network. Founder and president, Richard Stallman has also warned that cloud computing “will force people to buy into locked, proprietary systems that will cost more and more over time”.
 Key characteristics
- Agility improves with users’ ability to rapidly and inexpensively re-provision technological infrastructure resources.
- Cost is claimed to be greatly reduced and capital expenditure is converted to operational expenditure. This ostensibly lowers barriers to entry, as infrastructure is typically provided by a third-party and does not need to be purchased for one-time or infrequent intensive computing tasks. Pricing on a utility computing basis is fine-grained with usage-based options and fewer IT skills are required for implementation (in-house).
- Device and location independence enable users to access systems using a web browser regardless of their location or what device they are using (e.g., PC, mobile). As infrastructure is off-site (typically provided by a third-party) and accessed via the Internet, users can connect from anywhere.
- Multi-tenancy enables sharing of resources and costs across a large pool of users thus allowing for:
- Centralization of infrastructure in locations with lower costs (such as real estate, electricity, etc.)
- Peak-load capacity increases (users need not engineer for highest possible load-levels)
- Utilization and efficiency improvements for systems that are often only 10–20% utilized.
- Reliability improves through the use of multiple redundant sites, which makes cloud computing suitable for business continuity and disaster recovery. Nonetheless, many major cloud computing services have suffered outages, and IT and business managers can at times do little when they are affected.
- Scalability via dynamic (“on-demand”) provisioning of resources on a fine-grained, self-service basis near real-time, without users having to engineer for peak loads. Performance is monitored, and consistent and loosely-coupled architectures are constructed using web services as the system interface.
- Security could improve due to centralization of data, increased security-focused resources, etc., but concerns can persist about loss of control over certain sensitive data, and the lack of security for stored kernels. Security is often as good as or better than under traditional systems, in part because providers are able to devote resources to solving security issues that many customers cannot afford. Providers typically log accesses, but accessing the audit logs themselves can be difficult or impossible. Furthermore, the complexity of security is greatly increased when data is distributed over a wider area and / or number of devices.
- Sustainability comes about through improved resource utilization, more efficient systems, and carbon neutrality. Nonetheless, computers and associated infrastructure are major consumers of energy.
- 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.
See also category: Cloud clients
A cloud client consists of computer hardware and/or computer software that relies on cloud computing for application delivery, or that is specifically designed for delivery of cloud services and that, in either case, is essentially useless without it. For example:
- Mobile (Linux based – Palm Pre-WebOS Linux Kernel, Android-Linux Kernel, iPhone-Darwin Kernel, Microsoft based – Windows Mobile)
- Thin client (CherryPal, Wyse, Zonbu, gOS-based systems)
- Thick client / Web browser (Internet Explorer, Mozilla Firefox, Google Chrome, WebKit)
See also category: Cloud applications
A cloud application leverages cloud computing in software architecture, often eliminating the need to install and run the application on the customer’s own computer, thus alleviating the burden of software maintenance, ongoing operation, and support. For example:
- Peer-to-peer / volunteer computing (BOINC, Skype)
- Web applications (Webmail, Facebook, Twitter, YouTube, Yammer)
- Security as a service (MessageLabs, Purewire, ScanSafe, Zscaler)
- Software as a service (Envysion.com, A2Zapps.com, Google Apps, Salesforce,Learn.com, Zoho, BigGyan.com)
- Software plus services (Microsoft Online Services)
- Storage [Distributed]
See also category: Cloud platforms
A cloud platform (PaaS) delivers a computing platform and/or solution stack as a service, generally consuming cloud infrastructure and supporting cloud applications. It facilitates deployment of applications without the cost and complexity of buying and managing the underlying hardware and software layers. For example:
- Solution stacks
- Storage [Structured]
See also category: Cloud infrastructure
- Compute (Amazon CloudWatch, RightScale)
- Network (Amazon VPC)
- Storage [Raw] (Amazon EBS)
Cloud computing sample architecture
Cloud architecture, the systems architecture of the software systems involved in the delivery of cloud computing, comprises hardware and software designed by a cloud architect who typically works for a cloud integrator. It typically involves multiple cloud components communicating with each other over application programming interfaces, usually web services.
This closely resembles the Unix philosophy of having multiple programs each doing one thing well and working together over universal interfaces. Complexity is controlled and the resulting systems are more manageable than their monolithic counterparts.
Cloud storage architecture is loosely coupled, often assiduously avoiding the use of centralized metadata servers which can become bottlenecks. This enables the data nodes to scale into the hundreds, each independently delivering data to applications or users.
 Types by visibility
Cloud computing types
 Public cloud
Public cloud or external cloud describes cloud computing in the traditional mainstream sense, whereby resources are dynamically provisioned on a fine-grained, self-service basis over the Internet, via web applications/web services, from an off-site third-party provider who shares resources and bills on a fine-grained utility computing basis.
 Hybrid cloud
A hybrid cloud environment consisting of multiple internal and/or external providers “will be typical for most enterprises”. A hybrid cloud can describe configuration combining a local device, such as a Plug computer with cloud services. It can also describe configurations combining virtual and physical, colocated assets—for example, a mostly virtualized environment that requires physical servers, routers, or other hardware such as a network appliance acting as a firewall or spam filter.
 Private cloud
Private cloud and internal cloud are neologisms that some vendors have recently used to describe offerings that emulate cloud computing on private networks. These (typically virtualisation automation) products claim to “deliver some benefits of cloud computing without the pitfalls”, capitalising on data security, corporate governance, and reliability concerns. 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, essentially “[lacking] the economic model that makes cloud computing such an intriguing concept”.
While an analyst predicted in 2008 that private cloud networks would be the future of corporate IT, there is some uncertainty whether they are a reality even within the same firm. Analysts also claim that within five years a “huge percentage” of small and medium enterprises will get most of their computing resources from external cloud computing providers as they “will not have economies of scale to make it worth staying in the IT business” or be able to afford private clouds. Analysts have reported on Platform’s view that private clouds are a stepping stone to external clouds, particularly for the financial services, and that future datacenters will look like internal clouds.
The term has also been used in the logical rather than physical sense, for example in reference to platform as a service offerings, though such offerings including Microsoft‘s Azure Services Platform are not available for on-premises deployment.
 Types of services
Services provided by cloud computing can be split into three major categories:
 Infrastructure-as-a-Service (IaaS)
Infrastructure-as-a-Service(IaaS) like Amazon Web Services provides virtual servers with unique IP addresses and blocks of storage on demand. Customers benefit from an API from which they can control their servers. Because customers can pay for exactly the amount of service they use, like for electricity or water, this service is also called utility computing.
 Platform-as-a-Service (PaaS)
Platform-as-a-Service(PaaS) is a set of software and development tools hosted on the provider’s servers. Developers can create applications using the provider’s APIs. Google Apps is one of the most famous Platform-as-a-Service providers. Developers should take notice that there aren’t any interoperability standards (yet), so some providers may not allow you to take your application and put it on another platform.
 Software-as-a-Service (SaaS)
Software-as-a-Service (SaaS) is the broadest market. In this case the provider allows the customer only to use its applications. The software interacts with the user through a user interface. These applications can be anything from web based email, to applications like Twitter or Last.fm.
 Cloud Service Level Agreements (SLAS)
Most subscribers of a cloud service may feel as though they are getting into an arrangement where it appears as though vendors create the SLAs for their own protection against litigation, with minimal assurances to a tenant.
IT managers can focus on the following SLA tips with a vendor:
1) Data Protection: where there is a clear definition as to who will have access to the data and the levels of protection in effect for their data. Some questions that can be asked are : • How will data be encrypted? • How will compliance be addressed? • What are the levels of access control? • Will there be sub-contractors or third party providers processing the data? • Where are backups stored? • How is the data center secured? • What happens to the data if service providers are switched? • What processes are in place to mitigate legal inquiries about a customer’s data? • How often are audits done and what types of auditing tools are in place? • What happens to my data if there is an investigation taking place on another tenant sharing services and how will you ensure my access to my data in the event of equipment seizure by federal entities? • How is data deletion handled?
2) Continuity: one has to consider what happens in the event of an outage or another related event that causes data to become unavailable.
Some questions to consider here are • How will the vendor define a services outage? • Will there be scheduled vendor downtime for maintenance etc? • Will there be an alternative vendor hot site or vendor site prepped to take on load of access in the event of a vendor outage? • Are there tools in motion which will determine the severity of a vendor outage? • How will the tenant be compensated in the event of a vendor an outage? • Define levels of redundancy in place to minimize vendor outages?
3) Costs: on cost to consider are: • How is the vendor’s fee structured and are taxes and external fees accounted for in a vendor quote? • Will there be or are there current licensing fees above and beyond stated vendor service fees? • Will there be any hidden or add-on costs for vendor support? • How does the vendor structure their charges? Is it based upon usage,traffic or storage limit • Does the vendor offer price protection?
 Privacy, Security, and Standards Compliance
A major issue in cloud computing, especially with public clouds, is protection of user data. One concern is that cloud providers themselves may have access to customers’ unencrypted data – whether it’s on disk, in memory, or transmitted over the network. To limit this exposure, many sources recommend never giving providers access to unencrypted data or keys. A second concern is that many public cloud providers are unable or unwilling to allow auditing of their physical or network security measures. This can preclude them, and thus their customers, from meeting standards such as the US government’s HIPAA or Sarbanes-Oxley, the European Union’s Data Protection Directive, or the credit card industry’s PCI DSS. The extent of some public clouds across multiple legal jurisdictions further complicates this issue; see “Legal Issues” for more detail. These concerns are considered key obstacles to broader adoption of cloud computing, making them areas of active research and debate among cloud computing practitioners and advocates.
Critics of cloud computing cite its seemingly broad and vague definition. Oracle CEO Larry Ellison observes that cloud computing has been defined as “everything that we currently do” . Forrester VP Frank Gillett expresses similar criticism . Many technologies that have been branded as “cloud computing” have existed for a long time before the “cloud” label came into existence. Examples include databases , load balanced on-demand web hosting services , network storage , real time online services , hosted services in general , etc.
 See also
- Application service provider
- Cloud Computing Manifesto
- Managed Print Services
- Service-oriented architecture
- ^ “Cloud Computing: Clash of the clouds”. The Economist. 2009-10-15.
. Retrieved 2009-11-03.
- ^ Distinguishing Cloud Computing from Utility Computing
- ^ Gartner Says Cloud Computing Will Be As Influential As E-business
- ^ Gruman, Galen (2008-04-07). “What cloud computing really means”. InfoWorld.
. Retrieved 2009-06-02.
- ^ The Internet Cloud
- ^ Techtarget.com
- ^ “It’s probable that you’ve misunderstood ‘Cloud Computing’ until now”. TechPluto.
- ^ What’s In A Name? Utility vs. Cloud vs Grid
- ^ Cloud Computing: The Evolution of Software-as-a-Service
- ^ Forrester’s Advice to CFOs: Embrace Cloud Computing to Cut Costs
- ^ Five cloud computing questions
- ^ Nicholas Carr on ‘The Big Switch’ to cloud computing
- ^ 1 Midsize Organization Busts 5 Cloud Computing Myths
- ^ Cloud Computing Savings – Real or Imaginary?
- ^ Buyya, Rajkumar; Chee Shin Yeo, Srikumar Venugopal (PDF). Market-Oriented Cloud Computing: Vision, Hype, and Reality for Delivering IT Services as Computing Utilities. Department of Computer Science and Software Engineering, The University of Melbourne, Australia. pp. 9.
. Retrieved 2008-07-31.
- ^ Open source fuels growth of cloud computing, software-as-a-service
- ^ “Cloud computing—emerging paradigm for computing”.
- ^ July, 1993 meeting report from the IP over ATM working group of the IETF
- ^ Computeractive.co.uk
- ^ Internet Critic Takes on Microsoft
- ^ a b Jeff Bezos’ Risky Bet.
- ^ Layer8.net
- ^ Google and I.B.M. Join in ‘Cloud Computing’ Research
- ^ Keep an eye on cloud computing, Amy Schurr, Network World, 2008-07-08, citing the Gartner report, “Cloud Computing Confusion Leads to Opportunity”. Retrieved 2009-09-11.
- ^ Gartner Says Worldwide IT Spending On Pace to Surpass $3.4 Trillion in 2008, Gartner, 2008-08-18. Retrieved 2009-09-11.
- ^ Institutes Join Open Cirrus Cloud Test Bed
- ^ Feature Guide: Amazon EC2 Availability Zones
- ^ HP and Microsoft Plan to Advance Cloud computing
- ^ Guardian.co.uk
- ^ Infrastructure Agility: Cloud Computing as a Best Practice
- ^ Recession Is Good For Cloud Computing – Microsoft Agrees
- ^ a b c d Defining “Cloud Services” and “Cloud Computing”
- ^ The new geek chic: Data centers
- ^ Cloud Computing: Small Companies Take Flight
- ^ Google Apps Admins Jittery About Gmail, Hopeful About Future
- ^ New Resource, Born of a Cloud Feud
- ^ Exari: Death By Laptop
- ^ Encrypted Storage and Key Management for the cloud
- ^ Cloud computing security forecast: Clear skies
- ^ Google to go carbon neutral by 2008
- ^ What is Cloud Computing?
- ^ Shut off your computer
- ^ a b Nimbus Cloud Guide
- ^ Google’s Open Source Android OS Will Free the Wireless Web
- ^ In Sync to Pierce the Cloud
- ^ Microsoft demos mobile cloud sync client
- ^ CherryPal brings cloud computing to the masses
- ^ Zonbu has alluring features, price
- ^ GOS cloud computing
- ^ Google angles for business users with ‘platform as a service’
- ^ The Emerging Cloud Service Architecture
- ^ EMC buys Pi and forms a cloud computing group
- ^ Building GrepTheWeb in the Cloud, Part 1: Cloud Architectures
- ^ Cloud Maturity Is Accelerating: More Than Just Reaction To The Hype?
- ^ IBM Embraces Juniper For Its Smart ‘Hybrid Cloud’, Disses Cisco (IBM)
- ^ a b Private Clouds Take Shape
- ^ Blend the strengths of virtual and physical
- ^ Just don’t call them private clouds
- ^ There’s No Such Thing As A Private Cloud
- ^ Private cloud networks are the future of corporate IT
- ^ Private Cloud Computing: The Only Thing Real so Far is the Desire
- ^ Million-Dollar Private Clouds
- ^ From Grid to Cloud (IT-Tude.com)
- ^ Google opens private cloud to coders
- ^ Microsoft Nixes Private Azure Clouds
- ^ Cloud computing services
- ^ Faith-based IT doesn’t work in the cloud
- ^ Cloud Computing and the Constitution
- ^ Security Is Chief Obstacle To Cloud Computing Adoption, Study Says
- ^ Are security issues delaying adoption of cloud computing?
- ^ Larry Ellison – What The Hell Is Cloud Computing?
- ^ Oracle’s Ellison nails cloud computing
- ^ Cloud Computing is Hyped and Overblown, Forrester’s
- ^ Voice recognition gets “cloudy,” but is it the “new touch”?
- ^ a b The Rackspace Cloud™ Hosting Products
- ^ A trip into the secret, online ‘cloud’
- ^ Defining “Cloud Services” – an IDC update
- ^ What is cloud computing?
- David S. Linthicum: Cloud Computing and SOA Convergence in Your Enterprise: A Step-by-Step Guide, Addison-Wesley Professional, ISBN 0-13-600922-0
- George Reese: Cloud Application Architectures: Building Applications and Infrastructure in the Cloud, O’Reilly, ISBN 0-596-15636-7
- John Rhoton: Cloud Computing Explained: Implementation Handbook for Enterprises, Recursive Press, ISBN 0-9563556-0-9
- John Rittinghouse and James Ransome: Cloud Computing: Implementation, Management, and Security, CRC, ISBN 1-4398-0680-2
- Toby Velte, Anthony Velte and Robert Elsenpeter: Cloud Computing, A Practical Approach, McGraw-Hill Osborne Media, ISBN 0-07-162694-8
 External links
- Cloud Computing Risk Assessment (including recommendations) – November 2009, ENISA (with PDF file; 2 MB)
- M. D. Dikaiakos, D. Katsaros, G. Pallis, A. Vakali, P. Mehra: Guest Editors Introduction: “Cloud Computing, IEEE Internet Computing”, 12(5), Sep. 2009.
- San Murugesan (Editor), “Cloud Computing: IT’s Day in the Sun?”, Cutter Consortium, 2009.
- Luis M. Vaquero et al., A Break in the Clouds: Toward a Cloud Definition, ACM SIGCOMM Computer Communication Review, Volume 39, Issue 1 (January 2009), Pages 50–55, ISSN:0146-4833
- What is Cloud Computing ? – Web 2.0 expo – A video where Tim O’Reilly, Dan Farber, Matt Mullenweg and others answer this question.
- National Institute of Standards and Technology (USA) definition of cloud computing.
- Institutes Join Open Cirrus Cloud Test Bed 
- The Cloud Computing Tutorial.
- An introduction to Cloud Computing