• Infrastructure as a service (IaaS) comprises the cloud service model which provide access to computing resources in a virtualized environment “the cloud” across a network connection usually internet.
• IaaS is one of the three fundamental service models of cloud computing along with Platform as a service (PaaS) and Software as a service (SaaS)
• IaaS enables access to fundamental resources such as physical machines, virtual machines, virtual storage etc.
• Apart from these resources, the IaaS also offer Virtual machine disk storage, Virtual local area network (VLANs), Load balancers, IP addresses and software bundles etc.
• All the resources are made available to end user via server virtualization. Moreover, these resources are accessed by the customers as if they own them.
• Physically, the pool of hardware resource is pulled from a multitude of servers and networks usually distributed across numerous data centers, all of which the cloud provider is responsible for maintaining.
• The client, on the other hand, is given access to the virtualized components in order to build their own IT platforms.
• IaaS can be utilised by enterprise customers to create cost effective and easily scalable IT solutions where the complexities and expenses of managing the underlying hardware are outsourced to the cloud provider
• If the scale of a business customer’s operations fluctuate, or they are looking to expand, they can tap into the cloud resource as and when they need it rather than purchase, install and integrate hardware themselves.
• IaaS can be utilized in Enterprise Infrastructure, Cloud hosting, Virtual Data Centers (VDC) etc.

Features and Benefits of IaaS:

Location independence: the service can usually be accessed from any location as long as there is an internet connection and the security protocol of the cloud allows it

Physical security of data center locations: services available through a public cloud, or private clouds hosted externally with the cloud provider, benefit from the physical security afforded to the servers which are hosted within a data center

Scalability: resource is available as and when the client needs it and, therefore, there are no delays in expanding capacity or the wastage of unused capacity

Utility style costing: the service can be accessed on demand and the client only pays for the resource that they actually use

No single point of failure: if one server or network switch, for example, were to fail, the broader service would be unaffected due to the remaining multitude of hardware resources and redundancy configurations.  For many services if one entire data center were to go offline, never mind one server, the IaaS service could still run successfully.

No investment in hardware: the underlying physical hardware that supports an IaaS service is set up and maintained by the cloud provider, saving the time and cost of doing so on the client side.

Here are the characteristics of IaaS service model:

• On-demand availability of resources.
• Virtual machines with pre-installed software.
• Virtual machines with pre-installed Operating Systems such as Windows, Linux, and Solaris.
• The computing resources can be easily scaled up and down.
• Allows to store copies of particular data in different locations.

Drawbacks:

Data Erase Practices: The consumer uses virtual machines that in turn uses the common disk resources provided by the cloud provider. When the consumer releases the resource, the cloud provider must ensure that next consumer to rent the resource does not observe data residue from the previous consumer.

Compatibility with legacy security vulnerabilities: Because IaaS offers the consumer to run legacy software in provider's infrastructure, therefore it exposes consumers to all of the security vulnerabilities of such legacy software.

Robustness of VM-level isolation: IaaS offers an isolated environment to individual consumers through the hypervisor. The hypervisor is a software layer that includes hardware support for virtualization to split a physical computer into multiple virtual machines.

Virtual machine sprawl: The VM can become out of date with respect to security updates because IaaS allows the consumer to operate the virtual machines in running, suspended and off state. However, the provider can automatically update such VMs, but this mechanism is hard and complex.