Service Availability: Principles and Practice

Foreword

The need to keep systems and networks running 24 hours a day, seven days a week has never been greater, as these systems form some of the essential fabric of society ranging from business to social media. Keeping these systems running in the presence of hardware and software failures is defined as service availability. In some areas of networking, such as telecommunications, it has formed an essential requirement for almost 100 years; it is part of why traditional plain old telephone service (POTS) would still be available when power went out. With the advent of the Internet, service availability requirements are increasingly being demanded in the marketplace, not necessarily due to regulatory requirements, as was the case with telephone networks, but due to business requirements and pressures from the marketplace. Of course, it's not just communications where service availability is important, many other industries such as aerospace and defense have similar requirements. Imagine the impact of a loss of control during missile flight, for example.

After the Internet bubble of the late 1990s, and an almost global deregulation of the telecommunications market, it was increasingly recognized that the high cost of development for proprietary hardware and software systems was no longer viable. The future would increasingly be based on commercial off-the-shelf (COTS) systems, where time to market for new services, outweighs the elegance of proprietary hardware and software systems. ...