SaaS (Software as a Service)

● Direct consumption of an application by end users

● No inherent relationship to IaaS or PaaS but underlying infrastructure affects reliability and scalability of service

● Examples: Salesforce.com, Google Apps

PaaS (Platform as a Service)

● Typically additional services/abstraction layered on IaaS foundation

● Simplify development (e.g. app server services)

● Simplify operations (e.g. scaling with grid)

● Examples: Google App Engine, Force.com

IaaS (Infrastructure as a Service)

● Provision processing, storage, networking, and other computing resources

● Deployer configures and maintains operating systems, other software, and logical application “wiring”

● Examples: Private Clouds, Amazon EC2, IBM Business Test/Dev Cloud

Types of Cloud Computing's Clouds

1. Public Clouds: Service Provider owned and managed Access Over Web typically by per-per-use.

2. Private Clouds: Privately owned and managed with restricted Access (but could be hosted externally).

3. Hybrid Clouds: Interoperable combination of public and private clouds.

There are 3 cloud service types, namely:
SaaS: Software-As-A-Service (Applications, Processes, Information/Knowledge as a service)
PaaS: Platform-As-A-Service (virtualised optimised middlewares such as Operating systems, etc, etc)

IaaS: Infrastructure-As-A-Service (virtualised servers, storage and networks, etc).

AN “OFFICIAL” CLOUD DEFINITION

“...a model for enabling 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.”

- U.S. National Institute of Standards & Technology (NIST)