The 5-3-2 definition of cloud computing. Or is it 5-3-3?

One of the benefits of cloud computing or cloud IT services is that it got a fairly good definition from quite early on.  As opposed to a lot of other IT trends, developments and phenomena (Big Data, UGC, augmented reality anyone?).

The main definitions for cloud IT are based on the following 3 main principles or frameworks:

1. The "5 Essential Characteristics of Cloud Computing" by the National Institute of Standards and Technology (NIST)  in the “Definition of Cloud Computing” publication, namely
• On-demand and self-service
• Ubiquitous network access
• Location transparent resource pooling
• Rapid elasticity, and 
• Measured service with pay per use.
  
2. The three service stacks or the three service delivery methods for cloud IT, namely: 
• Software as a Service (SaaS): Applications delivered as-a-service to end-users in the fashion of the 5 main characteristics listed above
• Platform as a Service (PaaS): System, development and service platform delivered as-a-service, again based on key principles listed in 1, and
• Infrastructure (IaaS): Basic or fundamental IT services like processing, storage and networking delivered and utilized as-a-service, without the need for local HW install, management and involvement by the IT department.
  
3. The deployment or usage model for cloud IT, namely
• Private cloud: Access to and use of cloud IT service for private use only. i.e. for company internal or private home use only. Consumed from public cloud provider or based on internal or 3rd party DCs that are transparent towards the user.  And not Internet facing or exposed in general for general, public access
• Public cloud: General, Internet facing and exposed cloud-based IT service, accessible for anyone. A public IaaS or PaaS can be used to create a private cloud solution for instance in the SaaS-area.
• Hybrid cloud: For most companies it's hard to come by a IT solution that is strictly 100% private, internal only, or 100% public with no personal login or access.  This in turn led to the development of hybrid cloud IT services, where IT services hosted locally or by 3rd party were combined with public cloud service, and one can gain access to private cloud or on-prem IT services through public cloud gateway.
  And this leads to the "old" 5-3-2 cloud definition morphing into the 5-3-3 definition of cloud computing.

This 5-3-2 or now 5-3-3 definition was nicely formulated by Yung Chou of the Microsoft US Developer and Platform Evangelism Team, and illustrated by Chou in figure below.

Some of the listed principles and definitions merits a closer look and discussion besides the development of the hybrid cloud delivery model.

In many cases, one-company private cloud services evolved from IT departments having developed and were running highly efficient server virtualization solution on prem or in 3rd party DCs, and were adding self-serve, compute billing to internal business units, on-demand scaling etc to their service delivery.  As noted in a earlier post ("Where does cloud-based IT services and delivery come from?"), it was then easy to move to a 3rd party cloud service, most server hypervisors supporting transparent VM migration, load balancing or fail-over between on--prem VMs and VMs living with a cloud provider.

But in many cases we also have IT departments boasting that they already have done the cloud exercise when they have moved their server platform to a virtualization platform, and gaining increased management, quicker server deployment and service delivery as well as lower TCO/OPEX towards their users.  Looking at the NIST definition, many such IT shops are still missing self-serve support for business users, lack true cost-based IT accounting and pay per use billing, as well as location transparent resource pooling - many company IT platforms are single-location DCs, and there are built-in location or access restrictions.

Also the true nature of private cloud services seems to be up for debate.  While a public cloud solution are accessible and open for "anyone" based on shared, self-serve, pay as you go infrastructure, are a private cloud service dedicated to an organization inside a private data center or can it be on prem or hosted off premises by a 3rd party DC or hoster?  The answer is probably that all three ways can be used to create a private cloud solution.  Also, as noted above, a public cloud IaaS or PaaS service can in turn be used to provision a private PaaS or SaaS solution, when using reserved instances of VM for instance.