IaaS Definition
IaaS is short for Infrastructure As A Service.
Infrastructure as a Service refers to a combination of hosting, hardware, provisioning and basic services needed to run a cloud.
The IaaS is the part of the cloud computing architecture that provides access over the Internet. Bandwidth allocation and server resources are essential elements of IaaS. The IaaS architecture specifies dynamic scaling of bandwidth. A cloud computing installation should never be overwhelmed by peak demand, because the infrastructure service should be able to quickly add the resources needed to accommodate peak demand.
IaaS is sold as a metered service; you pay for only the bandwidth and other services your applications are using. Generally, fees are based on throughput but some vendors charge for server time, as well.