characteristics of cloud computing..

We can state that Cloud Computing allows business to increase IT capacity (or add capabilities) on the fly and in real time (Internet-enabled), without investing in new infrastructure, training new personnel or licensing new software, and as a pay-per-use service.
However, the above definition is not complete. Here is the NIST (National Institute of Standards and Technology) simplified version of Cloud Computing:

The five characteristics:

• On-demand self-service: individuals can set themselves up without needing anyone’s help;


• Ubiquitous network access: available through standard Internet-enabled devices;
• Location independent resource pooling: processing and storage demands are balanced across a common infrastructure with no particular resource assigned to any individual user;
• Rapid elasticity: consumers can increase or decrease capacity at will;
• Pay per use: consumers are charged fees based on their usage of a combination of computing power, bandwidth use and/or storage
The possible delivery models:

• Cloud Software as a Service (SaaS): Customers rent software hosted by the vendor;
• Cloud Platform as a Service (PaaS): Customers rent infrastructure and programming tools hosted by the vendor to create their own applications;
• Cloud Infrastructure as a Service (IaaS): Customers rent processing, storage,networking and other fundamental computing resources for all purposes.

The possible deployment models:

• Private cloud: The cloud infrastructure is owned or leased by a single organization and is operated solely for that organization.
• Community cloud: The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations).
• Public cloud: The cloud infrastructure is owned by an organization selling cloud services to the general public or to a large industry group.
• Hybrid cloud: The cloud infrastructure is a composition of two or more clouds (internal, community, or public) that remain unique entities but are bound together by standardized or proprietary technology).