**7.2 Cloud technologies**

Cloud computing is a prompt emerging technology that can be used by communication devices such as computers, tablets and smartphones [12]. Cloud computing is a model for enabling ubiquitous, convenient and on-demand network access to a common set of configurable computing resources (such as networks, servers, stores, applications and services) that can be provisioned and released quickly with minimal management effort or service provider interaction.

The architecture of cloud computing includes four layers: application, platforms, infrastructure and hardware (from top to bottom). The hardware layer consists of the cloud's physical resources (i.e. computer equipment such as servers). The infrastructure layer is also known as the 'virtualization layer' because it uses virtualization technologies to manage computing resources by partitioning physical resources. The platform layer consists of operating systems and application frameworks that reduce the burden on the virtual machine, and thus acts as a kind of virtualized server. The top layer is the application layer or the actual cloud application. These layers are loosely coupled so that each layer can evolve separately [13]. There are several methods of grouping cloud computing technology. Cloud computing can be split into four major groups:

