The telecommunications world is now moving rapidly towards SIP-based telephony and multimedia. The vision is to merge mobile and fixed networks into one coherent multimedia network. Ericsson has been a pioneer in SIP technology, and the first Erlang-based SIP stack was presented in 1999. A fortunate turn of events allowed us to revive the early SIP experiments, rewrite the software and experiment to find an optimal architecture, and later verify our implementation with great success in international interop events. We believe this to be a superb example of how a small team of experts, armed with advanced programming tools, can see their ideas through, with prototypes, field trials, and later large-scale industrial development.