Internet Engineering Task Force (IETF) A. Begen
Request for Comments: 7197 Cisco
Category: Standards Track Y. Cai
ISSN: 2070-1721 Microsoft
H. Ou
Cisco
April 2014
Duplication Delay Attribute in the Session Description Protocol
Abstract
A straightforward approach to provide protection against packet
losses due to network outages with a longest duration of T time units
is to 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
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7197.
Begen, et al. Standards Track [Page 1]RFC 7197 Duplication Delay Attribute in SDP April 2014Copyright Notice
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Table of Contents
1. Introduction ....................................................2
2. Requirements Notation ...........................................4
3. The 'duplication-delay' Attribute ...............................5
4. SDP Examples ....................................................6
5. Security Considerations .........................................7
6. IANA Considerations .............................................8
6.1. Registration of SDP Attributes .............................9
7. Acknowledgements ................................................9
8. References ......................................................9
8.1. Normative References .......................................9
8.2. Informative References ....................................10
1. Introduction
Inside an IP network, packet delivery may be interrupted due to
failure of a physical link, interface, or device. To reduce the
impact of such interruptions, some networks are built in a resilient
manner, allowing for multiple alternative paths between two
endpoints. However, if there is no resiliency in the network or the
failure happens in a non-resilient part of the network, a temporary
outage will occur (i.e., packets will get dropped). The outage will
last until network reconvergence takes place (i.e., until
connectivity is restored) around the failure. Typically, network
reconvergence takes between tens and hundreds of milliseconds,
depending on the size and features of the network.
There are a number of network-reconvergence technologies available
today, such as IP Fast Convergence, MPLS Traffic Engineering Fast
Reroute, and Multicast Only Fast Reroute. These technologies can be
augmented by different types of application-layer loss-repair methods
such as Forward Error Correction (FEC), retransmission, temporal
Begen, et al. Standards Track [Page 2]RFC 7197 Duplication Delay Attribute in SDP April 2014
redundancy, and spatial redundancy to minimize (and sometimes totally
eliminate) the impact of outages. Each combination has its distinct
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