✓ In contrast, private services  are provided inside a company’s firewall, enabling IT management to provide a self-service portal for employees and partners to easily access approved services. 

Characteristics of both models are covered in this section. 

## Renting 

When you purchase server and storage resources using IaaS services, you gain immediate access to the resources you need. You aren’t, however, renting the actual servers or other infrastructure. It’s not like a rental truck pulls up to your office to deliver the services. The physical components stay put in the infrastructure service provider’s data center. 

Within a private IaaS, renting takes on a different focus. Although you may not charge each user to access a resource, in the charge-back model, you can allocate usage fees to an individual department based on usage over a week, month, or year. Because of the flexibility of the IaaS model, the heaviest resource users can pay more than those who use fewer resources. 

## Self-service provisioning 

Self-service provisioning  is a key characteristic of IaaS that enables the user to obtain resources — such as servers and networking — through a self-service portal without relying on IT to provision these resources for them. The portal is similar to a banking ATM model that handles repetitive tasks easily through a self-service interface. 

## Dynamic scaling 

Dynamic scaling  occurs when resources can be automatically expanded or contracted based on the requirements of the workload or task. If users need more resources than expected, they can get them immediately. A provider or creator of IaaS typically optimizes the environment so the hardware, the operating system, and automation can support a huge number of workloads. 

## Service levels 

Many consumers acquire capacity based on an on-demand model with no contract. In other situations, the consumer signs a contract for a specific amount of storage and/or 

