Delayed Duplication Attribute in the Session Description Protocol
draft-ietf-mmusic-delayed-duplication-01
MMUSIC A. Begen
Internet-Draft Cisco
Intended status: Standards Track Y. Cai
Expires: September 21, 2013 Microsoft
H. Ou
Cisco
March 20, 2013
Delayed Duplication Attribute in the Session Description Protocol
draft-ietf-mmusic-delayed-duplication-01
Abstract
A straightforward approach to provide protection against packet
losses due to network outages with a longest duration of T time units
is to simply duplicate the original packets and send each copy
separated in time by at least T time units. This approach is
commonly referred to as Time-shifted Redundancy, Temporal Redundancy
or simply Delayed Duplication. This document defines an attribute to
indicate the presence of temporally redundant media streams and the
duplication delay in the Session Description Protocol.
Status of this Memo
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This Internet-Draft will expire on September 21, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . . 4
3. The 'duplication-delay' Attribute . . . . . . . . . . . . . . . 4
4. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Registration of SDP Attributes . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Consider that a media sender transmits an original source packet and
transmits its duplicate after a certain delay following the original
transmission. If a network outage hits the original transmission,
the expectation is that the second transmission arrives at the
receiver. Alternatively, the second transmission may be hit by an
outage and gets dropped, and the original transmission completes
successfully. On the receiver side, both transmissions can also
arrive and in that case, the receiver (or the node that does the
duplicate suppression) needs to identify the duplicate packets and
discard them appropriately, producing a duplicate-free stream.
Delayed duplication can be used in a variety of multimedia
applications where there is sufficient bandwidth for the duplicated
traffic and the application can tolerate the introduced delay.
However, it must be used with care since it might easily result in a
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