SER History

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,

Development is boosted by numerous newcomers joining in 2001 through 2003, many of those students to graduate later in Fokus. Extensions to SER are being developed  by Alex Hoffmann, Bogdan Iancu, Daniel Mierla, Jan Janak, SER's media counterpart SIP Express Media Server is built by Raphael Coeffic, Uli Abend, and Stephan Sayer; Nils Ohlmeier’s SIPSak diagnostic utility begins to climb open-source charts, and SERweb user interface appears courtesy of Karel Kozlik. SER goes to the SIP Interoperability Events (known formerly as bake-offs).

SER goes public: In September 2002, the code is publicly released under GPL. Same year, the first third-party contribution follows (ENUM from Juha Heinanen).

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, based in Berlin, Germany. serves the commercial users of SER software. The number of open source contributions grows up. 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 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". is started to host the documentation effort, FAQs, how-tos, and links.

First forki: Two former working group affiliates, created their own company located in Bucharest, Romania, and launched a SER fork known as "openser".

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,, the commercial activity is bought by its customer, Tekelec.

Expanding the team: Mid-2006, representatives of and agree to merge as the efforts of and are overlapping. needs access to developers to produce good documentation and needs better documentation.

New September 2006, the new combined effort 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 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.

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