Characteristics of Cloud Services – As Defined by ITIL

The ITIL 2011 refresh introduced a significant new appendix to the Service Strategy book titled Appendix C: Service Strategy and the Cloud.

This appendix is significant in that it clearly defines various types of cloud services and the types of clouds in use, as well as different aspects of cloud services. This post will focus on how this appendix describes the various aspects of cloud services.

Appendix C: Service Strategy and the Cloud indicates that there are five characteristics of cloud services. These characteristics are:

  • On demand
  • Ubiquitous access
  • Resource pooling
  • Rapid elasticity
  • Measured services

I’ll provide a brief description of each of these characteristics, as well as how I’ve recently seen companies offer services that meet these characteristics.

On Demand

An on demand service is a service that can be accessed when and where it’s needed through either the Internet or an Intranet. “On demand” literally means it’s available when the user demands it.

I recently completed an XSLT class. To do the assignments for this class, students activated a host with specific settings. Once the assignment was finished and uploaded to a website, the host was no longer needed, so it was deactivated until the student was ready to begin working on the next assignment. This was helpful because the class required significant configuration to make everything work. Having an on demand service like this meant that students could load a pre-configured environment as needed.

Ubiquitous Access

Ubiquitous access means that various types of clients can use the service. Ubiquitous access requires three things:

  1. The use of standard communication methods and network protocols
  2. Coarse grained interfaces
  3. An effective model for managing security-related aspects

An example of ubiquitous access includes services that allow users to store music, photos, or other information that can then be accessed by various devices such as traditional personal computers, tablets, and smartphones.

Resource Pooling

Cloud services are often provided through a collection of physical and virtual assets that are managed dynamically according to patterns of business activity and user and customer demand.

An example of resource pooling is having a collection of assets that can be quickly arranged as needed to meet customer demand. I once worked for a financial services company that pooled its hardware assets in such a way that we could utilize additional resources from the pool to quickly respond to demand for IT services.

Rapid Elasticity

A service that is elastic can be quickly and appropriately sized in-line with customer demand. What this means is that as patterns of business activity change, the demand for services is affected. A highly-elastic service is able to quickly add more resources in-line with increased demand or reduce resources in response to diminished demand.

Rapid elasticity has existed in IT for some time. An example of rapid elasticity I was recently exposed to was with respect to an IT organization’s network circuits. This organization moves large datasets across a portion of its network. At times, it requires more bandwidth and in order to achieve these needs dynamically reallocates networking circuits and assets. When the need for increased bandwidth diminishes, the organization positions network assets according to normal operating criteria.

Measured Services

Cloud services are often purchased according to a pay per use, or pay per utilization model. In order to offer that type of pricing arrangement, it is critical that there is some method to measure use of the service.

Measuring the utilization of services is nothing new. We’ve been doing it for quite a while in IT. An example of measuring a service comes from mainframe environments but has been used in other environments as well. Many organizations will calculate what is called a “MIPS rate”. “MIPS” stands for “million instructions per second”, and it is the number of instructions that a computer or service can execute per second. An MIPS rate will often not only consider this but also will weigh the average time various instructions take, consider the overall cost of providing the service, and ultimately produce a billing rate equal to the cost of 1 MIPS. I’ve worked with several organizations that billed internally for high-end computing resources in exactly this fashion.

In the most recent version of ITIL quite a bit of coverage is given to cloud-related topics and the impact of cloud technologies on IT service providers. The importance of this is to establish a common meaning of the various aspects of cloud services and how we as service providers can apply these technologies to deliver value to our customers.

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