Page 91 - Cloud computing: From paradigm to operation

Framework and requirements for cloud computing 1

The layering framework is shown diagrammatically in Figure 9-1.

Figure 9-1 – Cloud computing layering framework

Each of the layers in the framework is described in the following subclauses.
9.1.1.1 User layer

The user layer is the user interface through which a cloud service customer interacts with cloud service
provider and with cloud services, performs customer related administrative activities, and monitors cloud
services. It can also offer the output of cloud services to another resource layer instance.

9.1.1.2 Access layer
The access layer provides a common interface for both manual and automated access to the capabilities
available in the services layer. These capabilities include both the capabilities of the services and also the
administration and business capabilities.

The access layer is responsible for presenting cloud service capabilities over one or more access
mechanisms – for example, as a set of web pages accessed via a browser, or as a set of web services which
can be accessed programmatically, on secure communication. Another responsibility of the access layer is to
apply appropriate security functionality to the access to cloud service capabilities. The access layer is
responsible for authenticating the request through the use of user credentials and for validating the
authorization of the user to use particular capabilities. The access layer is also responsible for handling
encryption and checking for request integrity, where required.

The access layer can also be responsible for enforcing QoS policies on the traffic coming from the user layer
(e.g., service requests to the cloud service provider) and the traffic towards the user layer (e.g., output of
cloud services).
The access layer passes on validated requests to the components in the services layer. The access layer
accepts cloud service customer or cloud service provider's cloud service consumption requests to access
CSPs' services and resources.
9.1.1.3 Service layer

The service layer contains the implementation of the services provided by a cloud service provider. The
service layer contains and controls the software components that implement the services (but not the
underlying hypervisors, host operating systems, device drivers, etc.), and arranges to offer the cloud services
to users via the access layer.
The service implementation software in the service layer in turn relies upon the capabilities available in the
resource layer to provide the services that are offered and to ensure that the requirements of any SLA
relating to the services are met, for example, through the use of sufficient resources.

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