Session Initiation Protocol (SIP) Save
FAQs, background materials and lists of current work in this field.
http://www.cs.columbia.edu/sip/   

Brekeke Software Save
Products for small to medium sized offices and a server database.
http://www.brekeke.com/   

FirstHand Technologies Save
Client and server software developer for service providers and telecom equipment vendors, to address enterprise mobility markets.
http://www.firsthandtech.com/   

IETF SIP Charter Save
Working group for protocol development. Links to RFC's and internet drafts.
http://www.ietf.org/html.charters/sip...   

PROTOS Test Suite Save
A test-suite to find vulnerabilities in protocol software.
http://www.ee.oulu.fi/research/ouspg/...   

Parrish Systems Save
Sells off the shelf code and provides a software consultancy service.
http://www.parrishsys.com   

SIP Forum Save
A membership based forum. Also contains a news board.
http://www.sipforum.org/   

SIP Made Easy Save
An introductory tutorial talks about protocol functions, components, message types, how it works and where it is applied.
http://geocities.com/intro_to_multime...   

SIP Wiki Save
Wiki based resource containing information and links.
http://www.toyz.org/cgi-bin/sipwiki.cgi   

SIP411 Directory Services Save
A Yellow Pages style directory of SIP addresses.
http://www.sip411.com   

SIPfoundry Save
An international open source community providing VoIP solutions and technology based on the SIP standard.
http://www.sipfoundry.org/   

Soft Front Save
Provides a software development environment.
http://www.softfront.co.jp/en/   

Tech Invite Save
Portal containing links to technical information and RFC documentation.
http://www.tech-invite.com   

The SIP Center Save
Portal with technical and market resources aimed at commercial developers. Also provides a testbed area for software and proxy development.
http://www.sipcenter.com/   

Vidosystem Save
Produces softphones. Site has downloads section and information on protocols supported.
http://www.vidosystem.com   

VoIP User Save
Consumer guide and forum. Also has software phone downloads and links to service providers.
http://www.voipuser.org   

Voice System Save
Design, consultancy and development for SIP Express Router (SER) servers.
http://www.voice-sistem.ro   

pulver.com Save
A collection of information on the protocol. Contains news, reports and an IP telephony job noticeboard.
http://www.pulver.com/   

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