datatracker.ietf.org
Sign in
Version 5.3.0, 2014-04-12
Report a bug

Forward Error Correction Grouping Semantics in the Session Description Protocol
RFC 5956

Internet Engineering Task Force (IETF)                          A. Begen
Request for Comments: 5956                                         Cisco
Obsoletes: 4756                                           September 2010
Category: Standards Track
ISSN: 2070-1721

              Forward Error Correction Grouping Semantics
                  in the Session Description Protocol

Abstract

   This document defines the semantics for grouping the associated
   source and FEC-based (Forward Error Correction) repair flows in the
   Session Description Protocol (SDP).  The semantics defined in this
   document are to be used with the SDP Grouping Framework (RFC 5888).
   These semantics allow the description of grouping relationships
   between the source and repair flows when one or more source and/or
   repair flows are associated in the same group, and they provide
   support for additive repair flows.  SSRC-level (Synchronization
   Source) grouping semantics are also defined in this document for
   Real-time Transport Protocol (RTP) streams using SSRC multiplexing.

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/rfc5956.

Begen                        Standards Track                    [Page 1]
RFC 5956              FEC Grouping Semantics in SDP       September 2010

Copyright Notice

   Copyright (c) 2010 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 ....................................................3
   2. Requirements Notation ...........................................5
   3. Requirements and Changes from RFC 4756 ..........................5
      3.1. FEC Grouping Requirements ..................................5
      3.2. Source and Repair Flow Associations ........................6
      3.3. Support for Additivity .....................................6
   4. FEC Grouping ....................................................7
      4.1. "FEC-FR" Grouping Semantics ................................7
      4.2. SDP Example ................................................7
      4.3. FEC Grouping for SSRC-Multiplexed RTP Streams ..............9
      4.4. "FEC" Grouping Semantics ..................................10
      4.5. SDP Offer/Answer Model and RFC 4756
           Backward-Compatibility Considerations .....................11
   5. Security Considerations ........................................12
   6. IANA Considerations ............................................12
   7. Acknowledgments ................................................13
   8. References .....................................................13
      8.1. Normative References ......................................13
      8.2. Informative References ....................................14

Begen                        Standards Track                    [Page 2]
RFC 5956              FEC Grouping Semantics in SDP       September 2010

1.  Introduction

   Any application that needs a reliable transmission over an unreliable
   packet network has to cope with packet losses.  Forward Error
   Correction (FEC) is an effective approach that improves the
   reliability of the transmission, particularly in multicast and
   broadcast applications where the feedback from the receiver(s) is
   potentially limited.

   In a nutshell, FEC groups source packets into blocks and applies
   protection to generate a desired number of repair packets.  These
   repair packets may be sent on demand or independently of any receiver
   feedback.  The choice depends on the FEC scheme, the packet loss
   characteristics of the underlying network, the transport scheme

[include full document text]