November 04, 2008 - SERi  joins the sip-router project  Read more about it in the announcement .
SIP Express Router (SER) is a high-performance, configurable, free SIP server licensed under the open-source GNU license . It can act as SIP (RFC 3261 ) registrar, proxy or redirect server. SER can be configured to serve specialized purposes such as load balancing or SIP front-end to application servers, SEMS  for example. Together with the RTPproxy  software it can act as media relay or Session Border Controller.
SER features complete support of RFC 3261 functionality, a variety of database backends (mysql , oracle , postgres , radius, text-db), management features (remote management via XML-RPC , load-balancing), NATi  traversal, telephony features (LCR, speeddial), multidomain hosting, ENUM , presence , and even more .
SER is additionally enhanced by a variety of additional SIP tools , which provide functionality for management, media processing, CDRi  processing, etc.
SER is today default part of numerous operating systems and their distributions: Debian , FreeBSD , Gentoo , NetBSD, OpenBSD , OpenSUSE, Solaris .
SER history  spans back to the previous century. SER has been used since 2002 for various different purposes, frequently in the industry by major ISPs/ASPs and by universities to enable VoIPi  services. SER's particular strength is its performance (SER runs well even under heavy load caused by large subscriber populations or abnormal operational conditions), flexibility (SER's genuine configuration language and module interface allow high degree of customization) and interoperability (tested and operated against tens of SIP products over the years, including but not limited to (Microsoft, Cisco, Mitel, snom, Pingtel, Siemens, xten, and many others).
Today's SER is officially sponsored by former iptelorg.com Gmbh (now subsidiary of Tekelec ), iptego  Gmbh, FhG FOKUS , as well as multiple other companies who contribute in the forms of patches, modules, documentation, and community work on mailing lists etc.
iptel.org and all its projects are governed by the community through discussions on the mailing lists. Decisions are made through consensus. A common iptel.org technical board  is responsible for ensuring that the work in the different projects proceed smoothly and that any issues that cannot be handled through consensus are dealed with. Read more about management of iptel.org and it's projects .
Technical Information: C-Written. Ported to Linux (PC, IPAQ), BSD (PC) and Solaris (Sun). Throughput thousands of calls per second (CPSi ) on a dual-CPU PC (capacity needed to cover Bay Area) and hundreds of CPS on Compaq IPAQ. Support for both IPv4 and IPv6. Small footprint size: 300k core, all common modules (optional) up to 630k.
Have a look at Using SER  to get started.