Cloud Basic

Cloud 
A cloud refers to a distinct IT environment that is designed for the purpose of remotely provisioning scalable and measured IT resources. 

Cloud Service
A cloud service is any IT resource that is made remotely accessible via a cloud. Unlike other IT fields that fall under the service technology umbrella - such as service-oriented architecture - the term "service" within the context of cloud computing is especially broad. A cloud service can exist as a simple Web-based software program with a technical interface invoked via the use of a messaging protocol, or as a remote access point for administrative tools or larger environments and other IT resources.

Cloud service usage conditions are typically expressed in a service-level agreement (SLA) that is the human-readable part of a service contract between a cloud provider and cloud consumer that describes QoS features, behaviors, and limitations of a cloud-based service or other provisions.

An SLA provides details of various measurable characteristics related to IT outcomes, such as uptime, security characteristics, and other specific QoS features, including availability, reliability, and performance. Since the implementation of a service is hidden from the cloud consumer, an SLA becomes a critical specification.

Characterstics

Six specific characteristics are common to the majority of cloud environments:

1. On-Demand Usage
2. Ubiquitous Access
3. Multi-tenancy ( Resourcing Pooling)
4. Elasticity and Scalability
5. Measured Usage
6. Resiliency

Delivery Models

Here are the most common delivery models related to cloud computing:

• IaaS - Infrastructure as a Service (e.g., Oracle Cloud Infrastructure, Amazon Web Services)
• PaaS - Platform as a Service (e.g., Oracle Java Cloud Service, Google App Engine)
• SaaS - Software as a Service (e.g., Oracle Taleo, SalesForce.com)

Some of the more sophisticated offerings on the market derive directly from the aforementioned models:

• NaaS - Network as a Service (IaaS)
• iPaaS - Integration Platform as a Service (PaaS)
• DBaaS - Database as a Service (SaaS)

Deployment Models

These delivery models can be deployed and managed in a particular way, depending on access levels, permissions, resource availability, connectivity, security requirements and many other factors that will eventually shape the cloud offering’s deployment model of choice:

• Public Cloud - Multi-tenancy and resource pooling are maximized, because any cloud-based asset may be shared among a number of subscribers. Multiple organizations and particulars usually coexist in this model, though each tenant’s proprietary information can remain private and secure.
• Private Cloud – An organization owns, manages and provides a set of cloud-based resources, which will be ultimately used with diverse purposes by cloud consumers inside itself.
• Community Cloud – A group of organizations with a common nature and related goals can put together and manage cloud-based resources in a joint effort. Those resources can  be accessed and leveraged only by community members.
• Hybrid Cloud – A combination of two or more cloud offerings based on the  models described above. Regarding Oracle’s Cloud Adoption Strategy, this will be the case of most clients, which only enhances the need for a well-rounded Cloud Integration practice.

Cloud-to-cloud Integration

Source : http://whatiscloud.com/