I-D Action:draft-ietf-avt-rapid-acquisition-for-rtp-08.txt

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A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Audio/Video Transport Working Group of the IETF.


	Title           : Unicast-Based Rapid Acquisition of Multicast RTP Sessions
	Author(s)       : B. Ver Steeg, et al.
	Filename        : draft-ietf-avt-rapid-acquisition-for-rtp-08.txt
	Pages           : 54
	Date            : 2010-03-08

When an RTP receiver joins a multicast session, it may need to
acquire and parse certain Reference Information before it can process
any data sent in the multicast session.  Depending on the join time,
length of the Reference Information repetition (or appearance)
interval, size of the Reference Information as well as the
application and transport properties, the time lag before an RTP
receiver can usefully consume the multicast data, which we refer to
as the Acquisition Delay, varies and may be large.  This is an
undesirable phenomenon for receivers that frequently switch among
different multicast sessions, such as video broadcasts.

In this document, we describe a method using the existing RTP and
RTCP protocol machinery that reduces the acquisition delay.  In this
method, an auxiliary unicast RTP session carrying the Reference
Information to the receiver precedes/accompanies the multicast
stream.  This unicast RTP flow may be transmitted at a faster than
natural bitrate to further accelerate the acquisition.  The
motivating use case for this capability is multicast applications
that carry real-time compressed audio and video.  However, the
proposed method can also be used in other types of multicast
applications where the acquisition delay is long enough to be a
problem.

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