when one wants to select a subset of the conference participants to whom one's media is sent or from whom streams are received. Media filters are necessary to configure privacy of the participants in the conference. In analogy to broad-, multi-, any-, and swarm-casting, narrowcasting is a technique for limiting and focusing informa- tion streams. Narrowcasting systems extend broad- and multicasting systems by allowing media streams to be filtered-for relevancy control, privacy, and user interface optimization. We describe four narrowcasting commands: mute, deafen, select, and attend-to provide distributed privacy in SIP-based conferencing. Extensive development has been carried out in the area of conference and floor control [1,2]. Conventional features regarding media privacy in confer- ences are typically limited to scheduling and selecting the speaker. Advanced conferencing features such as adding/deleting participants, changing user agents (UAs) or modes (like switching from a desktop to a mobile phone), C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security TABLE 14.1 Three Different Mute Operations Self-mute PBX mute Narrowcasting mute (P2+P3+P4) (P3+P4) (P3+P4) (P1+P3+P4) (P2+P4) (P2+P3) - (P1+P2+P3) Self control. P1 Control by admin. P2P Control. P1 1 mutes mutes himself by P1 is muted by mod- P2. P2 may speak to turning off his mic so erator. P's media is not everyone, but P1 won't that no media goes to mixed in the media server. hear his voice. the media server, or P1 is in a listen-only, P1 can send a "self-mute" or "lurker" (stealth) mode. signal to the application server so that the media server simulates self- censorship. changing media, authenticating or authorizing participants, granting privi- leges, controlling presentation of media, sidebars, passive participants, whis- per/private messages, audio-only, and lecture mode are described in RFC 4597 [3]. Media privacy features allow participants to control their own infor- mation and to distribute their attention, 