{"draft":"draft-ietf-avt-rapid-acquisition-for-rtp-17","doc_id":"RFC6285","title":"Unicast-Based Rapid Acquisition of Multicast RTP Sessions","authors":["B. Ver Steeg","A. Begen","T. Van Caenegem","Z. Vax"],"format":["ASCII","HTML"],"page_count":"56","pub_status":"PROPOSED STANDARD","status":"PROPOSED STANDARD","source":"Audio\/Video Transport","abstract":"When an RTP receiver joins a multicast session, it may need to\r\nacquire and parse certain Reference Information before it can process\r\nany data sent in the multicast session.  Depending on the join time,\r\nlength of the Reference Information repetition (or appearance)\r\ninterval, size of the Reference Information, and the application and\r\ntransport properties, the time lag before an RTP receiver can\r\nusefully consume the multicast data, which we refer to as the\r\nAcquisition Delay, varies and can be large.  This is an undesirable\r\nphenomenon for receivers that frequently switch among different\r\nmulticast sessions, such as video broadcasts.\r\n\r\nIn this document, we describe a method using the existing RTP and RTP\r\nControl Protocol (RTCP) machinery that reduces the acquisition delay.\r\nIn this method, an auxiliary unicast RTP session carrying the\r\nReference Information to the receiver precedes or accompanies the\r\nmulticast stream.  This unicast RTP flow can be transmitted at a\r\nfaster than natural bitrate to further accelerate the acquisition.\r\nThe motivating use case for this capability is multicast applications\r\nthat carry real-time compressed audio and video.  However, this\r\nmethod can also be used in other types of multicast applications\r\nwhere the acquisition delay is long enough to be a problem.  \r\n[STANDARDS-TRACK]","pub_date":"June 2011","keywords":["[--------]","SSM","multicast","IPTV","fast channel change"],"obsoletes":[],"obsoleted_by":[],"updates":[],"updated_by":[],"see_also":[],"doi":"10.17487\/RFC6285","errata_url":null}