Broad Network Access

Although the cloud computing resources can be made available, they also need to be accessible. In order for users to start consuming the cloud services, they need to be able to access them. And the access needs to be supported from a variety of end-user platforms, such as laptops, desktops, tablets, and mobile phones, running various operating systems.

Because the cloud services are usually available remotely, and because the users are highly mobile, the access to these services needs to be protected (see Figure 21-6). Once the necessary secured access is provided, the services can be consumed over different private and public networks.

Figure 21-6 Broad Network Access Essential Characteristic

Cloud Computing Services

Cloud computing is about offering available computing resources to consumers (businesses, organizations, and people) in the form of services. The NIST has defined three types of services (see Figure 21-7) that can be used as a reference:

Figure 21-7 Cloud Computing Services

Infrastructure as a Service (IaaS)
Platform as a Service (PaaS)
Software as a Service (SaaS)

With the huge variety of services offered nowadays, the boundaries between them are becoming blurred. That’s why the term Everything as a Service (XaaS) can be used, even though it is not defined officially by the NIST.

The important point here is the “as a service” approach. When cloud services are offered “as a service,” the customer can plan their costs, as the services are metered. Having multiple different cost models provides flexibility in the way services are offered.

The relationship between the cloud provider and the cloud customer has additional parameters that can influence the cost. The most important parameter is the scope of responsibility of the provider and the customer. Depending on the category of services, the responsibilities of the provider can be limited only to the physical and virtual layers, and the customer is responsible for everything else, or the provider can be responsible for the whole application stack, as is the case of SaaS.