Subject: RFC 6285 on Unicast-Based Rapid Acquisition of Multicast RTP Sessions

From: [email-masked]
Date: Tue, 28 Jun 2011 15:36:39 -0700 (PDT)

A new Request for Comments is now available in online RFC libraries.

        RFC 6285

        Title:      Unicast-Based Rapid Acquisition of Multicast 
                    RTP Sessions 
        Author:     B. Ver Steeg, A. Begen,
                    T. Van Caenegem, Z. Vax
        Status:     Standards Track
        Stream:     IETF
        Date:       June 2011
        Mailbox:    [email-masked], 
                    [email-masked], 
                    [email-masked],  
                    [email-masked]
        Pages:      56
        Characters: 141497
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-avt-rapid-acquisition-for-rtp-17.txt

        URL:        http://www.rfc-editor.org/rfc/rfc6285.txt

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, and 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 can 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 RTP
Control Protocol (RTCP) machinery that reduces the acquisition delay.
In this method, an auxiliary unicast RTP session carrying the
Reference Information to the receiver precedes or accompanies the
multicast stream.  This unicast RTP flow can 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, this
method can also be used in other types of multicast applications
where the acquisition delay is long enough to be a problem.  
[STANDARDS-TRACK]

This document is a product of the Audio/Video Transport Working Group of the IETF.

This is now a Proposed Standard Protocol.

STANDARDS TRACK: This document specifies an Internet standards track
protocol for the Internet community,and requests discussion and suggestions
for improvements.  Please refer to the current edition of the Internet
Official Protocol Standards (STD 1) for the standardization state and
status of this protocol.  Distribution of this memo is unlimited.

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