Prehistoric period: Since 1995, a group of former students of the SIP co-inventor, Prof. Schulzrinne, undertakes active research in the VoIPi area at Fraunhofer Fokus (formerly known as GMD) in Berlin, Germany. The effort of the working group led by Dorgham Sisalem results in scientific publications, proof-of-content SIP implementations and consultancy to early industrial adopters of the technology. Jiri Kuthan's introductory VoIP webpage hosted by Fokus begins to be one of the most frequently cited source of information on SIP.
First line of code. In September 2001, first line of code of the SIP Express Router (SERi) is written by Andrei Pelinescu. By then, its routing feature was implemented using table-based first-match-first-found technique soon to be replaced by SER's routing language and enhanced by module interface for more rapid feature introduction. The working group's results are presented on a new website, iptel.org.
2003 is the year of adoption: People keep working on better and faster code. SER becomes leading open-source SIP proxy server and is quickly adopted by numerous SIP services, FWD and sipphone being the best known by then. New contributors emerge (Maxim Sobolev: nathelper, and Miklos Tirpak, later to join iptel: permissions).
Going out of lab: In 2004, SER is no longer lab work. It is a fully fledged SIP server adopted by numerous ISPs. In Germany, freenet and sipgate are the first adopters, other commercial services based on SER begin to emerge worldwide. The working group migrates from Fokus labs to a new company, iptelorg.com based in Berlin, Germany. Iptelorg.com serves the commercial users of SER software. The number of open source contributions grows up. iptelorg.com receives the rights to commercial use of the copyrights (similar to the dual licensing of mysql) and develops commercial extensions and other SIP-relatedi products for the professional SIP market. At the same time open-source community keeps benefiting of SER maintenance and development resulting from company's commercial activity. Copyright to modules and code developed by 3rd parties outside Fokus is kept by their respective owners.
The independent website iptel.org hosts the open-source SER, the free SIP service, and general SIP information. It is generously sponsored by several supporters including FOKUS Fraunhofer, iptelorg, and numerous individuals from the open source scene.
SER - Getting Started: Also in 2004, a documentation effort known as SER - Getting Started is started by three SER users from two continents. In first-half 2005, the first issue is made available describing how to get started with SER and best practices for seri.cfg, the configuration "language". ONsip.org is started to host the documentation effort, FAQs, how-tos, and links.
In 2005 corporate development is going on. iptelorg opens up a new development site in Prague, Czech Republic, with primary focus on development of SIP infrastructure for mobile service providers. Later this year, iptelorg.com, the commercial activity is bought by its customer, Tekelec.
Expanding the team: Mid-2006, representatives of iptel.org and ONsip.org agree to merge as the efforts of iptel.org and ONsip.org are overlapping. ONsip.org needs access to developers to produce good documentation and iptel.org needs better documentation.
New iptel.org: September 2006, the new combined effort iptel.org site is launched.
Next generation SER: In November 2006, a new release of SER, codenamed Ottendorf, addresses many structural shortcomings of previous SER based on experience with large-scale deployments. The release incorporates feedback from open source users and iptelorg.com customers. The key changes include update to SER's data model, rewriting of the important timers, TCP implementation, introduction of selects to address parts of SIP messages, as well as scalability and lots of bug fixes.