Siegfried Langenbach was the founder of Computer Service Langenbach GmbH, a German ISP. CSL was founded in 1972, specializing in statistical research, and added Internet activities in 1994. Langenbach was also involved in the creation of DENIC and foundational to ICANN, participating in one its earliest Board Committees. He was the first chair of its supervisory board. Langenbach was a member of Réseaux IP Européens (RIPE NCC), the Internet Council of Registrars (CORE), the Internet Engineering Task Force, and the Domain Name Supporting Organization (DNSO) application process. He passed away on September 27, 2005, at the age of 60.
- ICANN Membership Advisory Committee, providing the ICANN Board with possible membership structures for the election of At-Large Directors at Singapore meeting in March 1999.