Designing Quality into Software For The 5ESS(TM) Switch

The 5ESS(TM) switch is the most widely used digital switching system in the world today. In the United States alone, it switches some ten million of the country's 110 million telecommunications lines. Overseas, it is installed in Taiwan, Korea, the Netherlands, Saudi Arabia, the United Kingdom, and Colombia, South America. Two reasons for its popularity are its varsatility and reliability, both largely attributable to the quality of its software system. The 5ESS switch architecture is based on interlocking software modules that make it easy to use and to update, and hold its downtime to near-theoretical limits. This article describes the structure of the 5ESS(TM) software architecture and the processes employed to ensure continued high quality as new generic programs are developed for the system.