به طور معمول برای مفاهیم جدید تعاریف متعددی ارائه می شود که بعد از مدتی نظرات محققین در یک نقطه همگرا شده و در نهایت به یک تعریف با جوانب یکسان می رسند. در خصوص محاسبات ابری تاکنون تعریف واحدی ارائه نشده است. دانشگاه برکلی و موسسه ملی استاندارد و تکنولوژی آمریکا در این زمینه اقدام به بررسی دقیق و اخذ نظرات دانشمندان رایانه کرده و تعاریف جدیدی را مطرح کرده اند. آنچه در ادامه آورده می شود تعریف موسسه ملی استاندارد و تکنولوژی آمریکاست.

The NIST Definition of Cloud Computing 

1.  Introduction 

1.1  Authority 

The National Institute of Standards and Technology (NIST) developed this document in furtherance of its 

statutory responsibilities under the Federal Information Security Management Act (FISMA) of 2002, 

Public Law 107-347.  

 

NIST is responsible for developing  standards and guidelines, including minimum requirements, for 

providing adequate information security for all agency operations and assets; but such standards and 

guidelines shall not apply to national security systems.  This guideline is consistent with the requirements 

of the Office of Management and Budget (OMB) Circular A-130, Section 8b(3), “Securing Agency 

Information Systems,” as analyzed in A-130, Appendix IV: Analysis of Key Sections.  Supplemental 

information is provided in A-130, Appendix III.  

 

This guideline has been prepared for use by Federal agencies.  It may be used by nongovernmental 

organizations on a voluntary basis and is not subject to copyright, though attribution is desired. 

 

Nothing in this document should be taken to contradict standards and guidelines made mandatory and 

binding on Federal agencies by the Secretary of Commerce under statutory authority, nor should these 

guidelines be interpreted as altering or superseding the existing authorities of the Secretary of Commerce, 

Director of the OMB, or any other Federal official. 

 

1.2  Purpose and Scope 

Cloud computing is an evolving paradigm. The NIST definition characterizes important aspects of cloud 

computing and is intended to serve as a means for broad comparisons of cloud services and deployment 

strategies, and to provide a baseline for discussion from what is cloud computing to how to best use cloud 

computing.  The service and deployment models defined form a simple taxonomy that is not intended to 

prescribe or constrain any particular method of deployment, service delivery, or business operation. 

 

1.3  Audience 

The intended audience of this document is system planners, program managers, technologists, and others 

adopting cloud computing as consumers or providers of cloud services.   2 

2.  The NIST Definition of Cloud Computing 

Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared 

pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that 

can be rapidly provisioned and released with minimal management effort or service provider interaction. 

This cloud model is composed of five essential characteristics, three service models, and four deployment 

models. 

 

Essential Characteristics: 

On-demand self-service. A consumer can unilaterally provision computing capabilities, such as 

server time and network storage, as needed automatically without requiring human 

interaction with each service provider.  

Broad network access. Capabilities are available over the network and accessed through standard 

mechanisms that promote use by  heterogeneous  thin or thick  client platforms (e.g., 

mobile phones, tablets, laptops, and workstations). 

Resource pooling. The provider’s computing resources are pooled to serve multiple  consumers 

using a multi-tenant model, with different physical and virtual resources dynamically 

assigned and reassigned according to consumer demand. There is a sense of location 

independence in that the customer generally has no control or knowledge over the exact 

location of the provided resources but may be able to specify location at a higher level of 

abstraction (e.g., country, state, or datacenter). Examples of resources include storage, 

processing, memory, and network bandwidth. 

Rapid elasticity.  Capabilities can be elastically provisioned and released, in some cases 

automatically, to scale rapidly outward and  inward commensurate with demand. To the 

consumer, the capabilities available for provisioning often appear to be unlimited and can 

be appropriated in any quantity at any time. 

Measured service. Cloud systems automatically control and optimize resource use by leveraging 

a metering capability1

 at some level of abstraction appropriate to the type of service (e.g., 

storage, processing, bandwidth, and active  user  accounts). Resource usage can be 

monitored, controlled, and reported,  providing transparency for both the provider and 

consumer of the utilized service. 

 

Service Models: 

Software as a Service  (SaaS). The capability provided to the consumer is to use  the provider’s 

applications running on a cloud infrastructure

2

. The applications are accessible from 

various client devices through either a thin client interface, such as a web browser (e.g., 

web-based email), or a program interface. The consumer does not manage or control the 

underlying cloud infrastructure including network, servers, operating systems, storage, or 

even individual application capabilities, with the possible exception of limited  user-

specific application configuration settings. 

Platform as a Service (PaaS). The capability provided to the consumer is to deploy onto the cloud 

infrastructure consumer-created or acquired applications created using programming 

                                                       

1

 Typically this is done on a pay-per-use or charge-per-use basis. 

2

  A cloud infrastructure is the collection of hardware and software that enables the five essential characteristics of cloud 

computing. The cloud infrastructure can be viewed as containing both a physical layer and an abstraction layer. The physical 

layer consists of the hardware resources that are necessary to support the cloud services being provided, and typically includes 

server, storage and network components. The abstraction layer consists of the software deployed across the physical layer, 

which manifests the essential cloud characteristics.  Conceptually the abstraction layer sits above the physical layer.   3 

languages, libraries, services, and tools supported by the provider.

3

 The consumer does 

not manage or control the underlying cloud infrastructure including network, servers, 

operating systems, or storage, but has control over the deployed applications and possibly 

configuration settings for the application-hosting environment. 

Infrastructure as a Service  (IaaS).  The capability provided to the consumer is to provision 

processing, storage, networks, and other fundamental computing resources where the 

consumer is able to deploy and run arbitrary software, which can include operating 

systems and applications. The consumer does not manage or control the underlying cloud 

infrastructure but has control over operating systems, storage, and deployed applications; 

and possibly limited control of select networking components (e.g., host firewalls). 

 

Deployment Models: 

Private cloud. The cloud infrastructure is provisioned for exclusive use by a single organization 

comprising multiple  consumers (e.g., business units). It may be  owned, managed, and 

operated by the organization, a third party, or some combination of them, and it may exist 

on or off premises. 

Community  cloud.  The cloud infrastructure  is  provisioned  for  exclusive use by  a specific 

community  of consumers from organizations  that  have  shared concerns  (e.g., mission, 

security requirements,  policy,  and compliance considerations). It may be  owned, 

managed, and operated  by  one or more of  the organizations  in the community,  a third 

party, or some combination of them, and it may exist on or off premises. 

Public cloud. The cloud infrastructure is provisioned for open use by the general public. It may be 

owned, managed, and operated by a business, academic, or government organization, or 

some combination of them.  It exists on the premises of the cloud provider. 

Hybrid cloud. The cloud infrastructure is a  composition of two or more  distinct  cloud 

infrastructures (private, community, or public) that remain unique entities, but are bound 

together by standardized or proprietary technology that enables  data and application 

portability (e.g., cloud bursting for load balancing between clouds).