Cloud computing providers offer three models as defined by the National Institute of Standards and Technology (NIST), which is a non-regulatory federal agency acting under the U.S Department of Commerce. Service models are defined as the final commodity delivered to a client based on the extent to which the cloud computing ecosystem is partitioned. The different types of service models are the SaaS (Software as a service), PaaS (Platform as a service) and IaaS (Infrastructure as a service) models.
Software as a service (SaaS) is a model in which an application runs directly on the cloud and the user accesses it via the Internet. The service provider is responsible for the infrastructure and the associated maintenance costs. This makes the model extremely cost efficient and flexible for the end user, eliminating hardware and software requirements at the client’s end. However, this model has restrictions on the client’s application development freedom. Google Docs, Google Sheets are classic examples of SaaS. The SaaS model is most popular and holds the majority of the market share compared to other two models, due to ease of adaptability, good return on investment and reduced time to market.
Platform as a service (PaaS) provides the customer with the development environment including hardware and software tools for various phases of development and network connectivity. The users have the freedom to develop their own applications using the language of their choice without reliance on a web-based console. The caveat with this model is the interoperability of the application between different development environments. Amazon’s Relational Database services, Microsoft Azure are examples of this model.
Infrastructure as a Service (IaaS) gives the users the required instance of machine with storage and computational resource tailored to their need. The users have the freedom to provision the network infrastructure, operating system and storage capacity using web based console to meet their application requirements. The users have greater control over the virtual machine and are entirely responsible for the development environment including the installation of the operating system, the required software to develop the application and the timely software updates to the application. Amazon’s EC2 is a classic example of this type of service model.
All the three models are extremely efficient for both the cloud service provider and the customer, due to pay per-use model. Since the actual maintenance and the operating costs of the hardware are borne by the service provider, the customers benefit as they do not need to spend capital on maintenance costs while reaping the benefits of the cloud. In the recent times, these basic models have paved the way to newer vertical models like Business Process as a service (BPaaS), which automate certain fixed set of business services that are common across different customers and different departments within a single organization. In addition, it helps the customers leverage the various APIs in this model in order to customize specific services as per requirement.