Xten and Plantronics announced a partnership combining Xten's softphones with Plantronics full line of PC headsets. Xten has a FREE SIP softphone dubbed X-Lite, in addition to the fully featured X-PRO commercial softphone. The softphones are RFC3261 (SIP), RTP/RTCP (RFC 1889) and SDP (RFC 3264) compliant. http://www.xten.com