Cloud Computing

Definition

US National Institute of Standards and Technology defines Computing as 

       "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."

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.

Measured Service - 
Cloud systems automatically control and optimize resource use by leveraging a metering capability 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.

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.  

Features:

1. Massive Scale
2. Advanced Security
3. Resilient Computing
4. Homogeneity
5. Geographic Distribution
6. Virtualization
7. Service Orientation
8. Low Cost Software 

Cloud Service Models:

Cloud Models come in three types:

1.    SaaS (Software as a Service)

2.    IaaS (Infrastructure as a Service)

3.    PaaS (Platform as a Service)

Each of these cloud models has their own set of benefits that could serve the needs of various business.

Software as a Service (SaaS)

1. 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 a web browser (e.g., web-based email), or a program interface.

2. 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.e.g: Google Spreadsheet.

Infrastructure as a Service (IaaS)

1. The capability provided to provision processing, storage, networks, and other fundamental computing resources.

2. Consumer can deploy and run arbitrary software. e.g: Amazon Web Services and Flexi scale.

Platform as a Service (PaaS)

1. 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.

2. 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.

Pictorial Representation

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