A collection of information on the protocol. Contains news, reports and an IP telephony job noticeboard.

Portal with technical and market resources aimed at commercial developers. Also provides a testbed area for software and proxy development.

A membership based forum. Also contains a news board.

An international open source community providing VoIP solutions and technology based on the SIP standard.

A test-suite to find vulnerabilities in protocol software.

Client and server software developer for service providers and telecom equipment vendors, to address enterprise mobility markets.

Portal containing links to technical information and RFC documentation.

Consumer guide and forum. Also has software phone downloads and links to service providers.

Design, consultancy and development for SIP Express Router (SER) servers.

FAQs, background materials and lists of current work in this field.