From the Computer Utility to Cloud Computing - To the Cloud: Big Data in a Turbulent World - page 39

processing. If the provider is using a metric that reasonably relects the
service provided, then there is transparency for both provider and user.
Types of Cloud Computing
In addition to these characteristics of cloud services, one can identify
three different types of cloud service models that focus on infrastructure,
platform, and software, with each model providing the customer with
different levels of control. These are not inviolate categories but, in spite
of large gray areas at the margins, they are nevertheless useful in adding
a sense of what different types of cloud models aim to accomplish, from
simply providing a storage service to offering additional applications and
software for customers to use.
IaaS: Infrastructure as a Service. With this model, the cloud-service
provider manages a storage infrastructure for customer data, leaving the
customer to deploy its own software, including operating systems and
applications. Furthermore, under this model customers can control cer-
tain network components, like irewalls. It is ideal for repetitive uses that
require elasticity or the capacity to expand or contract quickly depending
on use. Examples include online gaming sites, online advertising networks,
video-sharing sites, and social-media applications.
PaaS: Platform as a Service . Here, in addition to offering storage facili-
ties, the cloud provider deploys onto the cloud infrastructure applications
that the customer has created or acquired using programming languages
and tools that the provider supports. Once again, the customer does not
manage the infrastructure; all of that is left to the cloud provider. Rather,
the customer gets to control the deployed applications. For example, the
city of Edmonton, Alberta, contracted with a cloud provider to create its
own tool, called Open Data Catalogue, which made information about
city services accessible to the public. The U.S. Department of Defense
(DOD) used a cloud provider when it needed to emulate battleield con-
ditions. In the latter case, DOD technical staff developed an application
on the Microsoft Azure platform.