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Lucent: 5ESS Telecommunications Switch

The 5ESStm product-line is a family of telephone switches that has an unparalleled reputation for reliability, quality, and performance. The switch was originally developed by AT&T Bell Labs and was first put into commercial use in 1982. It is currently made by Lucent Technologies. The majority of local telephone switches in the U.S. today are still 5ESS switches. If you live in the U.S. most likely when you pick up the handset on your telephone you are connected to a 5ESS switch.

Any particular switch in the product line is operated by approximately 10MLOC. The software architecture reflected in that code has remained relatively stable at the subsystem level over a period of 20 years, and was designed to accommodate a set of variabilities that can still be discerned by examining the architecture. In the early 1990s some of the first applications of domain engineering to a large, complex system were successfully accomplished in the 5ESS software and documented in the software engineering literature. Domains such as switch maintenance, signalling, and traffic management showed productivity improvements of factors of 3 to 5 as a result.


W. Howard, editor, “The 5ESS Switching System,” vol. 64, AT&T Technical Journal, July-August, 1985, Special Issue on the 5ESS Switch.


About This Product Line

Lucent was inducted into the Hall of Fame at theSecond Software Product Line Conference (SPLC2).

Cited improvements to the Lucent 5ESS Telecommunications Switch include productivity improvement (3x-5x) and high reliability and performance.