Jitsi is an open-source development project which is written in Java and is available here https://jitsi.org/Main/Download. Jitsi is a very mature project and the product is very feature rich and reliable. A very notable feature of Jitsi is it’s designed to be a business-class application and therefore has provisioning capabilities. What online provisioning facilitates is the capability for an administrator to configure and provision online a user’s pre-configured download. This is achieved through creation and customization of simple scripts.
Jitsi’s list of features includes support for all main communication protocols such as SIP, Googletalk, FaceBook, XMPP, .Net, Yahoo! Messenger, Aim and ICQ. By supporting all these protocols and services Jitsi can be used to consolidate all your messaging requirements under one platform. You will no longer have to change application to chat with friends on a different network they can all connect through Jitsi.
Furthermore, Jitsi supports presence, and one-to-one messaging on all protocols including SIP. Multi person chat and file transfer are also supported on all protocols listed above but unfortunately not on SIP. Instant messaging is secured via ODR encryption.
With regards Jitsi’s voice capabilities it can support audio calls, video calls, and both audio and video conferencing. Additionally it can handle both attended and blind call transfer, call recording and is one of the few SIP applications that addresses encryption. The data is encrypted for transfer using either SDES/SRTP or ZRTP encryption mechanisms.
Jitsi stores all passwords in encrypted format and uses a master password for access. It also supports TLS certification-based client authentication if required and encrypted both messaging and voice packets.
Jitsi has several other interesting features such as it can be integrated with Outlook so that presence shows and you can make calls, send messages, and chat, all from within Outlook or Apple address book. Additionally there is systray notifications, missed call notifications, and full call history.