Introduction
A paradigm for enabling network access to a scalable and elastic pool of shareable physical or virtual resources with self-service provisioning and administration on-demand
- (International Organization for Standardization, 2023)
Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, storage, servers, applications and services) that can be rapidly provisioned and released with minimum management effort or service provider interaction. (Mell & Grance, 2011)
The cloud model is composed of:
- 5 Essential Characteristics
- 3 Service Models
- 4 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 multi-tenant model, with different physical of virtual resources dynamically assigned or reassigned according to consumer demand.
There is a sense of location independence in that the costumer 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 capability (done on a pay-per-use basis) 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.
Cloud Infrastructure
It 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 the 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 servers, 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 later.
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. The applications are accessible from various client devices through either a thin client interface such as web browser (e.g., web based email), or a program interface.
The consumer does not manage or control the underlying cloud infrastructure including networks, 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 languages, libraries, services and tools supported by the provider.
The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed application 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, storage, deployed applications; and possibly limited control of select networking components (e.g., host firewalls) .
Deployment Models
Private cloud
The cloud infrastructure provisioned for exclusively 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 me 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 of proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).