Session Initiation Protocol (SIP) - FAQs, background materials and lists of current work in this field. Soft Front - Provides a software development environment. SIP Forum - A membership based forum. Also contains a news board. SIPfoundry - An international open source community providing VoIP solutions and technology based on the SIP standard. SIP (Session Initiation Protocol) Introduction - An introductory tutorial talks about protocol functions, components, message types, how it works and where it is applied. SIP Dojo - Information about SIP, technology around SIP, and SIP software products offered by Brekeke Software. PJSIP - An open-source multimedia communication library written in C, implementing protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. Understanding SIP exchanges by experimentation - The path of SIP signaling, SIP messages, transactions, and dialogs Session Initiation Protocol (sip) (concluded WG) - Working group for protocol development. Links to RFCs and internet drafts. PROTOS Test Suite - A test-suite to find vulnerabilities in protocol software. SIPVicious - Tools for auditing SIP devices: sip scanner listing SIP devices found on an IP range, online password cracker for SIP PBX.