MicroSIP is a portable SIP softphone based on the PJSIP stack available for Microsoft Windows. It facilitates high quality VoIP calls (p2p or on regular telephones) based on the open SIP protocol. MicroSIP falls into the free and open source software category and is being released under the GNU GPL-2.0-or-later. It relies on the PJSIP stack and draws on available features. This software's distinguishing characteristics are: Profile of a lightweight background application Small memory footprint (less than 20 MB RAM usage) Strong adherence to the SIP standard Support for a number of codecs: Opus, SILK, G.722, G.729, G.723.1, G.711, Speex, iLBC, GSM, AMR, AMR-WB, and video codecs H.264, H.263+, VP8. STUN and ICE NAT traversal SIP SIMPLE presence and messaging There are two variants, a full version with video and a "Lite" version for voice and messaging only. See also Comparison of VoIP software List of SIP software References External links Official website PJSIP official website MicroSIP Softphone Review at About.com reviews from portablefreeware community reviews from wilderssecurity community MDev Group website Free VoIP software Windows multimedia software