tribute lines URL containing a description of the session Time when the session is active E-mail address to obtain information about the session Times when the session will be repeated Phone number to obtain information about the session Media line Connection information Information about a media line For those of you particularly interested in this topic, the IETF is already evaluating some proposed extensions in the form of new a lines that will provide QoS when SIP and SDP are used together [draft-manyfolks]. SDP Next Generation (SDPng) Originally, SDP was designed to describe multimedia sessions in the Mbone, but now it is finding use in many other contexts. Among others, SDP is used with the Real-Time Streaming Protocol (RTSP) [RFC 2326] for streaming services, with SIP for conference invitations, and for devices with a master/slave configuration using Media Gateway Control Protocol (MGCP) [RFC 2705] or H.248. Because SDP was not designed for working The Internet Multimedia Conferencing Architecture in all these environments, it's an imperfect fit and lacks features needed by some applications. These new contexts, as well as a number of future applications that might need a session description mechanism, put new requirements [draft- kutscher-mmusic-sdpng-req] on the successor of SDP. Currently, this is called SDP next generation (SDPng) [draft-ietf-mmusic-sdpng] and is being developed in the Multiparty Multimedia Session Control (MMUSIC) work- ing group. SDPng will try to provide richer session descriptions and a bet- ter means for capability negotiation than SDP. However, one of the key concepts behind the design of SDPng is simplicity. Therefore, the trade-off is that SDPng must provide a reasonable level of functionality within a rea- sonable level of complexity. Real-Time Streaming Protocol (RTSP) The Real-Time Streaming Protocol (RTSP) [RFC 2326] is used to control multimedia servers, typically for streaming applications. The use of RTSP between an end user and a multimedia server can be compared to the