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Duplication Delay Attribute in the Session Description Protocol
RFC 7197

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 2014

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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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