Erlang

By Martin Heller

March 10, 2003

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In my December, 2002 column, I discussed the Lightweight Languages conference I attended at MIT in November. One of the languages presented there was Erlang, named after Agner Krarup Erlang (1878-1929), a Danish mathematician who developed a theory of stochastic processes in statistical equilibrium that is widely used in the telecommunications industry.

Joe Armstrong of the Distributed Systems Laboratory of the Swedish Institute of Computer Science gave the talk. Joe was and is one of the architects of the language and one of the authors of Concurrent Programming in ERLANG (Prentice Hall), along with Robert Virding, Claes Wikstrým, and Mike Williams.

A Little History

Erlang was designed for programming concurrent, real-time, distributed fault-tolerant systems. Erlang was designed in parallel with its first applications, in an internal project about languages for switching systems at Ericsson, the Swedish telecom giant. At first, Erlang was a secret project. Initially, it was slow, as the implementation was done on top of a Prolog interpreter; later, it was reimplemented with a compiler, on several operating systems and processors, and met its designers' performance goals.

Meanwhile, Ericsson, in its infinite wisdom, standardized on C++ for all its new projects, which led to Erlang becoming an open source language. One consequence was that the Erlang team left Ericsson for a startup. Another consequence of this is that one of Ericsson's biggest competitors, Nortel Networks, adopted Erlang for some of its own products, including the Alteon SSL Accelerator.

Meanwhile, back at Ericsson, some Erlang-based products that were already in progress when the "ban" went into effect came to market, including the AXD301, an ATM switch with 99.9999999 percent reliability (9 nines, or 31 ms. downtime a year!), which has captured 11% of the world market. The AXD301 system includes 1.7

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