draft-ietf-fecframe-raptor-01.txt   draft-ietf-fecframe-raptor-02.txt 
FEC Framework M. Watson FEC Framework M. Watson
Internet-Draft Qualcomm, Inc. Internet-Draft Qualcomm, Inc.
Intended status: Standards Track July 8, 2009 Intended status: Standards Track March 5, 2010
Expires: January 9, 2010 Expires: September 6, 2010
Raptor FEC Schemes for FECFRAME Raptor FEC Schemes for FECFRAME
draft-ietf-fecframe-raptor-01 draft-ietf-fecframe-raptor-02
Abstract
This document describes Fully-Specified Forward Error Correction
(FEC) Schemes for the Raptor and RaptorQ codes and their application
to reliable delivery of media streams in the context of FEC
Framework. The Raptor and RaptorQ codes are systematic codes, where
a number of repair symbols are generated from a set of source symbols
and sent in one or more repair flows in addition to the source
symbols that are sent to the receiver(s) within a source flow. The
Raptor and RaptorQ codes offer close to optimal protection against
arbitrary packet losses at a low computational complexity. Six FEC
Schemes are defined, two for protection of arbitrary packet flows,
two that are optimised for small source blocks and another two for
protection of a single flow that already contains a sequence number.
Repair data may be sent over arbitrary datagram transport (e.g. UDP)
or using RTP.
Status of this Memo Status of this Memo
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skipping to change at page 1, line 32 skipping to change at page 1, line 49
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Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
This document describes Fully-Specified Forward Error Correction described in the BSD License.
(FEC) Schemes for the Raptor code and its application to reliable
delivery of media streams in the context of FEC Framework. The
Raptor code is a systematic code, where a number of repair symbols
are generated from a set of source symbols and sent in one or more
repair flows in addition to the source symbols that are sent to the
receiver(s) within a source flow. The Raptor code offers a close to
optimal protection against arbitrary packet losses at a low
computational complexity. Two FEC Schemes are defined, one for
protection of arbitrary packet flows and another for protection of a
single flow that already contains a sequence number. Repair data may
be sent over arbitrary datagram transport (e.g. UDP) or using RTP.
An RTP Payload Type is defined for this latter case.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Document Outline . . . . . . . . . . . . . . . . . . . . . . . 5 2. Document Outline . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5 3. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5
4. Definitions and Abbreviations . . . . . . . . . . . . . . . . 5 4. Definitions and Abbreviations . . . . . . . . . . . . . . . . 5
4.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6
5. General procedures for Raptor FEC Schemes . . . . . . . . . . 6 5. General procedures for Raptor FEC Schemes . . . . . . . . . . 7
6. Raptor FEC Scheme for arbitrary packet flows . . . . . . . . . 8 6. Raptor FEC Schemes for arbitrary packet flows . . . . . . . . 8
6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 8 6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 8 6.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 8
6.2.1. FEC Framework Configuration Information . . . . . . . 8 6.2.1. FEC Framework Configuration Information . . . . . . . 8
6.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 9 6.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 9
6.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 9 6.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 10
6.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 10 6.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3.1. Source symbol construction . . . . . . . . . . . . . . 10 6.3.1. Source symbol construction . . . . . . . . . . . . . . 11
6.3.2. Repair packet construction . . . . . . . . . . . . . . 10 6.3.2. Repair packet construction . . . . . . . . . . . . . . 11
6.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 11 6.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 12
7. Optimised Raptor FEC Scheme for arbitrary packet flows . . . . 11 7. Optimised Raptor FEC Scheme for arbitrary packet flows . . . . 12
7.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 12
7.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 12 7.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 13
7.2.1. FEC Framework Configuration Information . . . . . . . 12 7.2.1. FEC Framework Configuration Information . . . . . . . 13
7.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 12 7.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 13
7.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 12 7.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 13
7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 12 7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 13
7.3.1. Source symbol construction . . . . . . . . . . . . . . 12 7.3.1. Source symbol construction . . . . . . . . . . . . . . 13
7.3.2. Repair packet construction . . . . . . . . . . . . . . 12 7.3.2. Repair packet construction . . . . . . . . . . . . . . 13
7.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 13 7.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 14
8. Raptor FEC Scheme for a single sequenced flow . . . . . . . . 13 8. Raptor FEC Scheme for a single sequenced flow . . . . . . . . 14
8.1. Formats and codes . . . . . . . . . . . . . . . . . . . . 13 8.1. Formats and codes . . . . . . . . . . . . . . . . . . . . 14
8.1.1. FEC Framework Configuration Information . . . . . . . 13 8.1.1. FEC Framework Configuration Information . . . . . . . 14
8.1.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 13 8.1.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 15
8.1.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 13 8.1.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 15
8.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 14 8.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 16
8.2.1. Source symbol construction . . . . . . . . . . . . . . 14 8.2.1. Source symbol construction . . . . . . . . . . . . . . 16
8.2.2. Derivation of Source FEC Packet Identification 8.2.2. Derivation of Source FEC Packet Identification
Information . . . . . . . . . . . . . . . . . . . . . 15 Information . . . . . . . . . . . . . . . . . . . . . 16
8.2.3. Repair packet construction . . . . . . . . . . . . . . 16 8.2.3. Repair packet construction . . . . . . . . . . . . . . 17
8.2.4. Procedures for RTP source flows . . . . . . . . . . . 16 8.2.4. Procedures for RTP source flows . . . . . . . . . . . 18
8.3. FEC Code Specification . . . . . . . . . . . . . . . . . . 16 8.3. FEC Code Specification . . . . . . . . . . . . . . . . . . 18
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10. Session Description Protocol (SDP) Signaling . . . . . . . . . 16 10. Session Description Protocol (SDP) Signaling . . . . . . . . . 18
11. Congestion Control Considerations . . . . . . . . . . . . . . 17 11. Congestion Control Considerations . . . . . . . . . . . . . . 19
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12.1. Registration of FEC Scheme IDs . . . . . . . . . . . . . . 17 12.1. Registration of FEC Scheme IDs . . . . . . . . . . . . . . 19
13. Normative References . . . . . . . . . . . . . . . . . . . . . 17 13. Normative References . . . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
The FEC Framework [I-D.ietf-fecframe-framework] describes a framework The FEC Framework [I-D.ietf-fecframe-framework] describes a framework
for the application of Forward Error Correction to arbitrary packet for the application of Forward Error Correction to arbitrary packet
flows. Modelled after the FEC Building Block developed by the IETF flows. Modelled after the FEC Building Block developed by the IETF
Reliable Multicast Transport working group ([RFC5052]), the FEC Reliable Multicast Transport working group [RFC5052], the FEC
Framework defines the concept of FEC Schemes which provide specific Framework defines the concept of FEC Schemes which provide specific
Forward Error Correction schemes. This document describes two FEC Forward Error Correction schemes. This document describes six FEC
Schemes which make use of the Raptor FEC code as defined in Schemes which make use of the Raptor and RaptorQ FEC codes as defined
[RFC5053]. in [RFC5053] and [I-D.ietf-rmt-bb-fec-raptorq].
The FEC protection mechanism is independent of the type of the source The FEC protection mechanism is independent of the type of the source
data, which can be an arbitrary sequence of packets, including for data, which can be an arbitrary sequence of packets, including for
example audio or video data. In general, the operation of the example audio or video data. In general, the operation of the
protection mechanism is as follows: protection mechanism is as follows:
o The sender determines a set of source packets (a source block) to o The sender determines a set of source packets (a source block) to
be protected together based on the FEC Framework Configuration be protected together based on the FEC Framework Configuration
Information. Information.
o The sender arranges the source packets into a set of source o The sender arranges the source packets into a set of source
symbols, each of which is the same size. symbols, each of which is the same size.
o The sender applies the Raptor protection operation on the source o The sender applies the Raptor protection operation on the source
symbols to generate the required number of repair symbols. symbols to generate the required number of repair symbols.
o The sender packetizes the repair symbols and sends the repair o The sender packetizes the repair symbols and sends the repair
packet(s) along with the source packets to the receiver(s). packet(s) along with the source packets to the receiver(s).
Per the FEC Framework requirements, the sender MUST transmit the Per the FEC Framework requirements, the sender MUST transmit the
source and repair packets in different source and repair flows, source and repair packets in different source and repair flows, or in
respectively. At the receiver side, if all of the source packets are the case RTP transport is used for Repair packets, in different RTP
streams. At the receiver side, if all of the source packets are
successfully received, there is no need for FEC recovery and the successfully received, there is no need for FEC recovery and the
repair packets are discarded. However, if there are missing source repair packets are discarded. However, if there are missing source
packets, the repair packets can be used to recover the missing packets, the repair packets can be used to recover the missing
information. information.
The operation of the FEC mechanism requires that the receiver can The operation of the FEC mechanism requires that the receiver can
identify the relationships between received source packets and repair identify the relationships between received source packets and repair
packets and in particular which source packets are missing. In many packets and in particular which source packets are missing. In many
cases, data already exists in the source packets which can be used to cases, data already exists in the source packets which can be used to
refer to source packets and to identify which packets are missing. refer to source packets and to identify which packets are missing.
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purposes in the form of a non-empty FEC Source Payload ID. This case purposes in the form of a non-empty FEC Source Payload ID. This case
if referred to as the "arbitrary packet flow" case. Accordingly, if referred to as the "arbitrary packet flow" case. Accordingly,
this document defines two FEC Schemes, one for the case of a single this document defines two FEC Schemes, one for the case of a single
sequenced flow and another for the case of arbitrary packet flows. sequenced flow and another for the case of arbitrary packet flows.
2. Document Outline 2. Document Outline
This document is organised as follows: This document is organised as follows:
Section 5 defines general procedures applicable to the use of the Section 5 defines general procedures applicable to the use of the
Raptor code in the context of the FEC Framework. Raptor and RaptorQ codes in the context of the FEC Framework.
Section 6defines an FEC Scheme for the case of arbitrary source Section 6defines an FEC Scheme for the case of arbitrary source
flows and follows the format defined for FEC Schemes in flows and follows the format defined for FEC Schemes in
[I-D.ietf-fecframe-framework]. This scheme is equivalent to that [I-D.ietf-fecframe-framework]. When used with Raptor codes, this
defined in [3GPP MBMS Specification]. scheme is equivalent to that defined in [MBMSTS].
Section 7 defines an FEC Scheme similar to that defined in Section 7 defines an FEC Scheme similar to that defined in
Section 6but with optimisations for the case where only limited Section 6but with optimisations for the case where only limited
source block sizes are required. This scheme is equivalent to source block sizes are required. When used with Raptor codes,
that defined in [dvbts] for arbitrary packet flows. this scheme is equivalent to that defined in [dvbts] for arbitrary
packet flows.
Section 8 defines an FEC Scheme for the case of a single flow Section 8 defines an FEC Scheme for the case of a single flow
which is already provided with a source packet sequence number. which is already provided with a source packet sequence number.
This scheme is equivalent to that defined in [dvbts] for the case When used with Raptor codes, this scheme is equivalent to that
of a single sequenced flow. defined in [dvbts] for the case of a single sequenced flow.
3. Requirements Notation 3. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
4. Definitions and Abbreviations 4. Definitions and Abbreviations
The definitions, notations and abbreviations commonly used in this The definitions, notations and abbreviations commonly used in this
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4. Definitions and Abbreviations 4. Definitions and Abbreviations
The definitions, notations and abbreviations commonly used in this The definitions, notations and abbreviations commonly used in this
document are summarized in this section. document are summarized in this section.
4.1. Definitions 4.1. Definitions
This document uses the following definitions. For further This document uses the following definitions. For further
definitions that apply to FEC Framework in general, see definitions that apply to FEC Framework in general, see
[I-D.ietf-fecframe-framework]. [I-D.ietf-fecframe-framework].
Source Flow: The packet flow(s) carrying the source data and to Source Flow: The packet flow(s) or stream(s) carrying the source
which FEC protection is to be applied. data and to which FEC protection is to be applied.
Repair Flow: The packet flow(s) carrying the repair data. Repair Flow: The packet flow(s) or stream(s) carrying the repair
data.
Symbol: A unit of data. Its size, in bytes, is referred to as the Symbol: A unit of data. Its size, in bytes, is referred to as the
symbol size. symbol size.
Source Symbol: The smallest unit of data used during the encoding Source Symbol: The smallest unit of data used during the encoding
process. process.
Repair Symbol: Repair symbols are generated from the source symbols. Repair Symbol: Repair symbols are generated from the source symbols.
Source Packet: Data packets that contain only source symbols. Source Packet: Data packets that contain only source symbols.
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o FSSI: FEC-Scheme-Specific Information. o FSSI: FEC-Scheme-Specific Information.
o SS-FSSI: Sender-Side FEC-Scheme-Specific Information. o SS-FSSI: Sender-Side FEC-Scheme-Specific Information.
o RS-FSSI: Receiver-Side FEC-Scheme-Specific Information. o RS-FSSI: Receiver-Side FEC-Scheme-Specific Information.
5. General procedures for Raptor FEC Schemes 5. General procedures for Raptor FEC Schemes
This section specifies general procedures which apply to all Raptor This section specifies general procedures which apply to all Raptor
FEC Schemes, specifically the construction of source symbols from a and RaptorQ FEC Schemes, specifically the construction of source
set of source transport payloads. As described in symbols from a set of source transport payloads. As described in
[I-D.ietf-fecframe-framework] for each Application Data Unit in a [I-D.ietf-fecframe-framework] for each Application Data Unit in a
source block, the FEC Scheme is provided with: source block, the FEC Scheme is provided with:
o A description of the source data flow with which the Application o A description of the source data flow with which the Application
Data Unit is associated and an integer identifier associated with Data Unit is associated and an integer identifier associated with
that flow. that flow.
o The Application Data Unit itself. o The Application Data Unit itself.
o The length of the Application Data Unit. o The length of the Application Data Unit.
skipping to change at page 8, line 23 skipping to change at page 8, line 27
packet. Thus, the Encoding Symbol ID value associated with the j-th packet. Thus, the Encoding Symbol ID value associated with the j-th
source packet, ESI[j], is given by ESI[j] = 0, for j=0 and ESI[j] = source packet, ESI[j], is given by ESI[j] = 0, for j=0 and ESI[j] =
sum{s[i], i=0,...,(j-1)}, for 0 < j < n. sum{s[i], i=0,...,(j-1)}, for 0 < j < n.
Source blocks are identified by integer Source Block Numbers. This Source blocks are identified by integer Source Block Numbers. This
specification does not specify how Source Block Numbers are allocated specification does not specify how Source Block Numbers are allocated
to source blocks. The Source FEC Packet Identification Information to source blocks. The Source FEC Packet Identification Information
consists of the identity of the source block and the Encoding Symbol consists of the identity of the source block and the Encoding Symbol
ID associated with the packet. ID associated with the packet.
6. Raptor FEC Scheme for arbitrary packet flows 6. Raptor FEC Schemes for arbitrary packet flows
6.1. Introduction 6.1. Introduction
This section specifies an FEC Scheme for the application of the This section specifies an FEC Scheme for the application of the
Raptor code to arbitary packet flows. This scheme is recommended in Raptor and RaptorQ codes to arbitary packet flows. This scheme is
scenarios where maximal generality is required. recommended in scenarios where maximal generality is required.
This scheme is equivalent to that specified in [3GPP MBMS When used with Raptor codes, this scheme is equivalent to that
Specification]. specified in [MBMSTS].
6.2. Formats and Codes 6.2. Formats and Codes
6.2.1. FEC Framework Configuration Information 6.2.1. FEC Framework Configuration Information
6.2.1.1. FEC Scheme ID 6.2.1.1. FEC Scheme ID
The value of the FEC Scheme ID for the fully-specified FEC scheme The value of the FEC Scheme ID for the fully-specified FEC scheme
defined in this section is XXX, as assigned by IANA. defined in this section is XXX when [RFC5053] is used and YYY when
[I-D.ietf-rmt-bb-fec-raptorq] is used, as assigned by IANA.
6.2.1.2. Scheme-Specific Elements 6.2.1.2. Scheme-Specific Elements
The scheme-specific elements of the FEC Framework Configuration The scheme-specific elements of the FEC Framework Configuration
information for this scheme are as follows: information for this scheme are as follows:
Maximum Source Block Length A non-negative integer less than 2^13, Maximum Source Block Length Name: "Kmax", Value range: A decimal
in units of symbols non-negative integer less than 8192 (for Raptor) or 56405 (for
RaptorQ), in units of symbols
Encoding Symbol Size A non-negative integer less than 2^16, in units Encoding Symbol Size Name: "T", Value range: A decimal non-
of bytes negative integer less than 65536, in units of bytes
An encoding format for this information in a 4 octet field is defined Payload ID Format Name: "P", Value range: "A" or "B"
as follows:
An encoding format for The Maximum Source Block Length and Encoding
Symbol Size is defined below.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Symbol Size (T) | Max. Source Block Length | | Symbol Size (T) |Max. Source Block Length (Kmax)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P| Reserved |
+-+-+-+-+-+-+-+-+
Figure 1: FEC Scheme Specific Information Figure 1: FEC Scheme Specific Information
The P bit shall be set to zero to indicate Format A or to 1 to
indicate Format B. The last octet of the above encoding may be
omitted, in which case Format A shall be assumed.
The Payload ID Format identifier defines which of the Source FEC
Payload ID and Repair FEC Payload ID formats defined below shall be
used. Payload ID Format B SHALL NOT be used when[RFC5053] is used.
6.2.2. Source FEC Payload ID 6.2.2. Source FEC Payload ID
This scheme makes use of an Explicit Source FEC Payload ID, which is This scheme makes use of an Explicit Source FEC Payload ID, which is
appended to the end of the source packets. appended to the end of the source packets. Two formats are defined
for the Source FEC Payload ID, format A and format B. The format that
is used is signalled as part of the FEC Framework Configuration
Information
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Number (SBN) | Encoding Symbol ID (ESI) | | Source Block Number (SBN) | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Source FEC Payload ID Figure 2: Source FEC Payload ID - Format A
Source Block Number (SBN), (16 bits): An integer identifier for the Source Block Number (SBN), (16 bits): An integer identifier for the
source block that the source data within the packet relates to. source block that the source data within the packet relates to.
Encoding Symbol ID (ESI), (16 bits): The starting symbol index of Encoding Symbol ID (ESI), (16 bits): The starting symbol index of
the source packet in the source block. the source packet in the source block.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SBN | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Source FEC Payload ID - Format B
Source Block Number (SBN), (8 bits): An integer identifier for the
source block that the source data within the packet relates to.
Encoding Symbol ID (ESI), (24 bits): The starting symbol index of
the source packet in the source block
6.2.3. Repair FEC Payload ID 6.2.3. Repair FEC Payload ID
The structure of the Repair FEC Payload ID is defined below: Two formats for the Repair FEC Payload ID, Format A and Format B are
defined below:
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Number (SBN) | Encoding Symbol ID (ESI) | | Source Block Number (SBN) | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Length (SBL) | | Source Block Length (SBL) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Repair FEC Payload ID Repair FEC Payload ID - Format A
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SBN | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Length (SBL) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Repair FEC Payload ID - Format B
Source Block Number (SBN), (16 bits) An integer identifier for the Source Block Number (SBN), (16 bits) An integer identifier for the
source block that the repair symbols within the packet relate to. source block that the repair symbols within the packet relate to.
Encoding Symbol ID (ESI), (16 bits) Integer identifier for the Encoding Symbol ID (ESI), (16 bits) Integer identifier for the
encoding symbols within the packet. encoding symbols within the packet.
Source Block Length (SBL), (16 bits) The number of source symbols in Source Block Length (SBL), (16 bits) The number of source symbols in
the source block. the source block.
skipping to change at page 10, line 35 skipping to change at page 11, line 34
Identifier and Source Block Length is defined by the FEC Code Identifier and Source Block Length is defined by the FEC Code
Specification. Specification.
6.3. Procedures 6.3. Procedures
6.3.1. Source symbol construction 6.3.1. Source symbol construction
This FEC Scheme uses the procedures defined in Section 5 to construct This FEC Scheme uses the procedures defined in Section 5 to construct
a set of source symbols to which the FEC code can be applied. The a set of source symbols to which the FEC code can be applied. The
sender MUST allocate Source Block Numbers to source blocks sender MUST allocate Source Block Numbers to source blocks
sequentially, wrapping around to zero after Source Block Number sequentially, wrapping around to zero after Source Block Number 65535
2^16-1. (Format A) or 255 (Format B).
During the construction of the source block: During the construction of the source block:
o the length indication, l[i], included in the Source Packet o the length indication, l[i], included in the Source Packet
Information for each packet shall be the transport payload length. Information for each packet shall be the transport payload length.
o the value of s[i] in the construction of the Source Packet o the value of s[i] in the construction of the Source Packet
Information for each packet shall be the smallest integer such Information for each packet shall be the smallest integer such
that s[i]*T >= (l[i]+3). that s[i]*T >= (l[i]+3).
skipping to change at page 11, line 17 skipping to change at page 12, line 17
where I_repair is the index of the repair symbol in the sequence of where I_repair is the index of the repair symbol in the sequence of
repair symbols generated according to Section 6.4, where the first repair symbols generated according to Section 6.4, where the first
repair symbol has index 0, the second index 1 etc. and SBL is the repair symbol has index 0, the second index 1 etc. and SBL is the
Source Block Length. The Source Block Length field of the Repair FEC Source Block Length. The Source Block Length field of the Repair FEC
Payload ID field SHALL be set to the number of symbols included in Payload ID field SHALL be set to the number of symbols included in
the Source Packet Information of packets associated with the source the Source Packet Information of packets associated with the source
block. block.
6.4. FEC Code Specification 6.4. FEC Code Specification
The Raptor FEC encoder defined in [RFC5053] SHALL be used. The The Raptor FEC encoder defined in [RFC5053] or
source symbols passed to the Raptor FEC encoder SHALL consist of the [I-D.ietf-rmt-bb-fec-raptorq] SHALL be used. The source symbols
source symbols constructed according to Section 6.3.1. Thus the passed to the Raptor FEC encoder SHALL consist of the source symbols
value of the parameter K used by the FEC encoder (equal to the Source constructed according to Section 6.3.1. Thus the value of the
Block Length) may vary amongst the blocks of the stream but SHALL NOT parameter K used by the FEC encoder (equal to the Source Block
Length) may vary amongst the blocks of the stream but SHALL NOT
exceed the Maximum Source Block Length signalled in the FEC Scheme- exceed the Maximum Source Block Length signalled in the FEC Scheme-
specific information. The symbol size, T, to be used for source specific information. The symbol size, T, to be used for source
block construction and the repair symbol construction is equal to the block construction and the repair symbol construction is equal to the
Encoding Symbol Size signaled in the FEC Scheme Specific Information. Encoding Symbol Size signaled in the FEC Scheme Specific Information.
7. Optimised Raptor FEC Scheme for arbitrary packet flows 7. Optimised Raptor FEC Scheme for arbitrary packet flows
7.1. Introduction 7.1. Introduction
This section specifies a slightly modified version of the FEC Scheme This section specifies a slightly modified version of the FEC Scheme
skipping to change at page 12, line 15 skipping to change at page 13, line 16
This scheme is equivalent to that specified in [dvbts] for arbitrary This scheme is equivalent to that specified in [dvbts] for arbitrary
packet flows. packet flows.
7.2. Formats and Codes 7.2. Formats and Codes
7.2.1. FEC Framework Configuration Information 7.2.1. FEC Framework Configuration Information
7.2.1.1. FEC Scheme ID 7.2.1.1. FEC Scheme ID
The value of the FEC Scheme ID for the fully-specified FEC scheme The value of the FEC Scheme ID for the fully-specified FEC scheme
defined in this section is XXX, as assigned by IANA. defined in this section is XXX when [RFC5053] is used and YYY when
[I-D.ietf-rmt-bb-fec-raptorq] is used, as assigned by IANA.
7.2.1.2. FEC Scheme specific information 7.2.1.2. FEC Scheme specific information
See . (Section 6.2.1.2) See . (Section 6.2.1.2)
7.2.2. Source FEC Payload ID 7.2.2. Source FEC Payload ID
See . (Section 6.2.2) See . (Section 6.2.2)
7.2.3. Repair FEC Payload ID 7.2.3. Repair FEC Payload ID
skipping to change at page 13, line 7 skipping to change at page 14, line 7
Where I_repair is the index of the repair symbol in the sequence of Where I_repair is the index of the repair symbol in the sequence of
repair symbols generated according to Section 6.4, where the first repair symbols generated according to Section 6.4, where the first
repair symbol has index 0, the second index 1 etc. and MSBL is the repair symbol has index 0, the second index 1 etc. and MSBL is the
Maximum Source Block Length signalled in the FEC Scheme Specific Maximum Source Block Length signalled in the FEC Scheme Specific
Information. The Source Block Length field of the Repair FEC Payload Information. The Source Block Length field of the Repair FEC Payload
ID field SHALL be set to the number of symbols included in the Source ID field SHALL be set to the number of symbols included in the Source
Packet Information of packets associated with the source block. Packet Information of packets associated with the source block.
7.4. FEC Code Specification 7.4. FEC Code Specification
The Raptor FEC encoder defined in [RFC5053] SHALL be used. The The Raptor FEC encoder defined in [RFC5053] or
source symbols passed to the Raptor FEC encoder SHALL consist of the [I-D.ietf-rmt-bb-fec-raptorq] SHALL be used. The source symbols
source symbols constructed according to Section 6.3.1 extended with passed to the Raptor FEC encoder SHALL consist of the source symbols
zero or more padding symbols such that the total number of symbols in constructed according to Section 6.3.1 extended with zero or more
the source block is equal to the Maximum Source Block Length signaled padding symbols such that the total number of symbols in the source
in the FEC Scheme Specific Information. Thus the value of the block is equal to the Maximum Source Block Length signaled in the FEC
parameter K used by the FEC encoded is equal to the Maximum Source Scheme Specific Information. Thus the value of the parameter K used
Block Length for all blocks of the stream. Padding symbols shall by the FEC encoded is equal to the Maximum Source Block Length for
consist entirely of bytes set to the value zero. The symbol size, T, all blocks of the stream. Padding symbols shall consist entirely of
to be used for source block construction and the repair symbol bytes set to the value zero. The symbol size, T, to be used for
construction is equal to the Encoding Symbol Size signaled in the FEC source block construction and the repair symbol construction is equal
Scheme Specific Information. The parameter T shall be set such that to the Encoding Symbol Size signaled in the FEC Scheme Specific
the number of source symbols in any source block is at most KMAX = Information.
8192. The Maximum Source Block Length parameter - and hence the
number of symbols used in the FEC Encoding and Decoding operations - When [RFC5053] is used, the parameter T SHALL be set such that the
SHALL be set to one of the following values: number of source symbols in any source block is at most 8192. The
Maximum Source Block Length parameter - and hence the number of
symbols used in the FEC Encoding and Decoding operations - SHALL be
set to one of the following values:
101, 120, 148, 164, 212, 237, 297, 371, 450, 560, 680, 842, 1031, 101, 120, 148, 164, 212, 237, 297, 371, 450, 560, 680, 842, 1031,
1139, 1281 1139, 1281
When [I-D.ietf-rmt-bb-fec-raptorq] is used, the parameter T SHALL be
set such that the number of source symbols in any source block is
less than 56404. The Maximum Source Block Length parameter SHALL be
set to one of the supported vaoues for K' defined in Section 5.6 of
[I-D.ietf-rmt-bb-fec-raptorq].
8. Raptor FEC Scheme for a single sequenced flow 8. Raptor FEC Scheme for a single sequenced flow
8.1. Formats and codes 8.1. Formats and codes
8.1.1. FEC Framework Configuration Information 8.1.1. FEC Framework Configuration Information
8.1.1.1. FEC Scheme ID 8.1.1.1. FEC Scheme ID
The value of the FEC Scheme ID for the fully-specified FEC scheme The value of the FEC Scheme ID for the fully-specified FEC scheme
defined in this section is XXX, as assigned by IANA. defined in this section is XXX when [RFC5053] is used and YYY when
[I-D.ietf-rmt-bb-fec-raptorq] is used, as assigned by IANA.
8.1.1.2. Scheme-specific elements 8.1.1.2. Scheme-specific elements
See Section 6.2.1.2 See Section 6.2.1.2
8.1.2. Source FEC Payload ID 8.1.2. Source FEC Payload ID
The Source FEC Payload ID field is not used by this FEC Scheme. The Source FEC Payload ID field is not used by this FEC Scheme.
Source packets are not modified by this FEC Scheme. Source packets are not modified by this FEC Scheme.
8.1.3. Repair FEC Payload ID 8.1.3. Repair FEC Payload ID
The Repair FEC Payload ID format for this FEC Scheme is shown below: Two formats for the Repair FEC Payload ID are defined, Format A and
Format B.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initial Sequence Number | Encoding Symbol ID | | Initial Sequence Number | Encoding Symbol ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Length | | Source Block Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Repair FEC Payload ID Figure 4: Repair FEC Payload ID - Format A
Initial Sequence Number (Flow i ISN) - 16 bits This field specifies
the lowest 16 bits of the sequence number of the first packet to
be included in this sub-block. If the sequence numbers are
shorter than 16 bits then the received Sequence Number SHALL be
logically padded with zero bits to become 16 bits in length
respectively.
Encoding Symbol ID (ESI) - 16 bits This field indicates which repair
symbols are contained within this repair packet. The ESI provided
is the ESI of the first repair symbol in the packet.
Source Block Length (SBL) - 16 bits This field specifies the length
of the source block in symbols.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initial Sequence Number | Source Block Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoding Symbol ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Repair FEC Payload ID - Format B
Initial Sequence Number (Flow i ISN) - 16 bits This field specifies Initial Sequence Number (Flow i ISN) - 16 bits This field specifies
the lowest 16 bits of the sequence number of the first packet to the lowest 16 bits of the sequence number of the first packet to
be included in this sub-block. If the sequence numbers are be included in this sub-block. If the sequence numbers are
shorter than 16 bits then the received Sequence Number SHALL be shorter than 16 bits then the received Sequence Number SHALL be
logically padded with zero bits to become 16 bits in length logically padded with zero bits to become 16 bits in length
respectively. respectively.
Encoding Symbol ID (ESI) - 16 bits This field indicates which repair Encoding Symbol ID (ESI) - 16 bits This field indicates which repair
symbols are contained within this repair packet. The ESI provided symbols are contained within this repair packet. The ESI provided
skipping to change at page 14, line 36 skipping to change at page 16, line 26
Source Block Length (SBL) - 16 bits This field specifies the length Source Block Length (SBL) - 16 bits This field specifies the length
of the source block in symbols. of the source block in symbols.
8.2. Procedures 8.2. Procedures
8.2.1. Source symbol construction 8.2.1. Source symbol construction
This FEC Scheme uses the procedures defined in Section 5 to construct This FEC Scheme uses the procedures defined in Section 5 to construct
a set of source symbols to which the FEC code can be applied. The a set of source symbols to which the FEC code can be applied. The
sender MUST allocate Source Block Numbers to source blocks sender MUST allocate Source Block Numbers to source blocks
sequentially, wrapping around to zero after Source Block Number sequentially, wrapping around to zero after Source Block Number 65535
2^16-1. in the case Format A is used for FEC Payload IDs and 255 in the case
Format B is used for FEC Payload IDs.
During the construction of the source block: During the construction of the source block:
o the length indication, l[i], included in the Source Packet o the length indication, l[i], included in the Source Packet
Information for each packet shall be dependent on the protocol Information for each packet shall be dependent on the protocol
carried within the transport payload. Rules for RTP are specified carried within the transport payload. Rules for RTP are specified
below. below.
o the value of s[i] in the construction of the Source Packet o the value of s[i] in the construction of the Source Packet
Information for each packet shall be the smallest integer such Information for each packet shall be the smallest integer such
skipping to change at page 16, line 20 skipping to change at page 18, line 11
8.2.3. Repair packet construction 8.2.3. Repair packet construction
See Section 7.3.2 See Section 7.3.2
8.2.4. Procedures for RTP source flows 8.2.4. Procedures for RTP source flows
In the specific case of RTP source packet flows, then the RTP In the specific case of RTP source packet flows, then the RTP
Sequence Number field SHALL be used as the sequence number in the Sequence Number field SHALL be used as the sequence number in the
procedures described above. The length indication included in the procedures described above. The length indication included in the
Application Data Unit Information SHALL be the RTP payload length Application Data Unit Information SHALL be the RTP payload length
plus the length of the CSRCs, if any, and the RTP padding bytes, if plus the length of the CSRCs, if any, the RTP Header Extension, if
any. Note that this length is always equal to the UDP payload length present, and the RTP padding bytes, if any. Note that this length is
of the packet minus 12. always equal to the UDP payload length of the packet minus 12.
8.3. FEC Code Specification 8.3. FEC Code Specification
See Section 7.4 See Section 7.4
9. Security Considerations 9. Security Considerations
For the general security considerations related to the use of FEC, For the general security considerations related to the use of FEC,
refer to [I-D.ietf-fecframe-framework]. refer to [I-D.ietf-fecframe-framework]. No security considerations
specific to this document have been identified.
10. Session Description Protocol (SDP) Signaling 10. Session Description Protocol (SDP) Signaling
This section provides an SDP [RFC4566] example. The following This section provides an SDP [RFC4566] example. The following
example uses the SDP elements for FEC Framework, which were example uses the SDP elements for FEC Framework, which were
introduced in [I-D.ietf-fecframe-sdp-elements], and the FEC grouping introduced in [I-D.ietf-fecframe-sdp-elements], and the FEC grouping
semantics [RFC4756]. semantics [I-D.ietf-mmusic-rfc4756bis].
In this example, we have one source video stream (mid:S1) and one FEC In this example, we have one source video stream (mid:S1) and one FEC
repair stream (mid:R1). We form one FEC group with the "a=group:FEC repair stream (mid:R1). We form one FEC group with the "a=group:FEC
S1 R1" line. The source and repair streams are sent to the same port S1 R1" line. The source and repair streams are sent to the same port
on different multicast groups. The repair window is set to 200 ms. on different multicast groups. The repair window is set to 200 ms.
v=0 v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=Raptor FEC Example s=Raptor FEC Example
t=0 0 t=0 0
a=group:FEC S1 R1 a=group:FEC S1 R1
m=video 30000 RTP/AVP 100 m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127 c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000 a=rtpmap:100 MP2T/90000
a=fec-source-flow: id=0; tag-len=4 a=fec-source-flow: id=0; tag-len=4
a=mid:S1 a=mid:S1
m=application 30000 udp/fec m=application 30000 udp/fec
c=IN IP4 233.252.0.2/127 c=IN IP4 233.252.0.2/127
a=fec-repair-flow: encoding-id=0; fssi=5hu= a=fec-repair-flow: encoding-id=0; fssi=Kmax:8192,T:128,P:A
a=repair-window: 200 a=repair-window:200
a=mid:R1 a=mid:R1
11. Congestion Control Considerations 11. Congestion Control Considerations
For the general congestion control considerations related to the use For the general congestion control considerations related to the use
of FEC, refer to [I-D.ietf-fecframe-framework]. of FEC, refer to [I-D.ietf-fecframe-framework].
12. IANA Considerations 12. IANA Considerations
12.1. Registration of FEC Scheme IDs 12.1. Registration of FEC Scheme IDs
The value of FEC Scheme IDs is subject to IANA registration. For The value of FEC Scheme IDs is subject to IANA registration. For
general guidelines on IANA considerations as they apply to this general guidelines on IANA considerations as they apply to this
document, refer to [I-D.ietf-fecframe-framework]. document, refer to [I-D.ietf-fecframe-framework].
This document registers three values in the FEC Framework (FECFRAME) This document registers three values in the FEC Framework (FECFRAME)
FEC Encoding IDs registry as follows: FEC Encoding IDs registry as follows:
o XXX for the Raptor FEC Scheme for Arbitrary Packet Flows o XXX for the Raptor FEC Scheme for Arbitrary Packet Flows
(Section 6. (Section 6 using Raptor [RFC5053].
o XXX for the Raptor FEC Scheme for Arbitrary Packet Flows
(Section 6 using RaptorQ [I-D.ietf-rmt-bb-fec-raptorq].
o XXX for the Optimised Raptor FEC Scheme for Arbitrary Packet Flows o XXX for the Optimised Raptor FEC Scheme for Arbitrary Packet Flows
(Section 7). (Section 7) using Raptor [RFC5053].
o XXX for the Optimised Raptor FEC Scheme for Arbitrary Packet Flows
(Section 7) using RaptorQ [I-D.ietf-rmt-bb-fec-raptorq].
o XXX for the Raptor FEC Scheme for a single sequence flow o XXX for the Raptor FEC Scheme for a single sequence flow
(Section 8). (Section 8) using Raptor [RFC5053].
o XXX for the Raptor FEC Scheme for a single sequence flow
(Section 8) using RaptorQ [I-D.ietf-rmt-bb-fec-raptorq].
13. Normative References 13. Normative References
[I-D.ietf-fecframe-framework] [I-D.ietf-fecframe-framework]
Watson, M., "Forward Error Correction (FEC) Framework", Watson, M., "Forward Error Correction (FEC) Framework",
draft-ietf-fecframe-framework-03 (work in progress), draft-ietf-fecframe-framework-06 (work in progress),
October 2008. March 2010.
[I-D.ietf-fecframe-sdp-elements] [I-D.ietf-fecframe-sdp-elements]
Begen, A., "SDP Elements for FEC Framework", Begen, A., "SDP Elements for FEC Framework",
draft-ietf-fecframe-sdp-elements-03 (work in progress), draft-ietf-fecframe-sdp-elements-04 (work in progress),
June 2009. August 2009.
[RFC5052] Watson, M., Luby, M., and L. Vicisano, "Forward Error [RFC5052] Watson, M., Luby, M., and L. Vicisano, "Forward Error
Correction (FEC) Building Block", RFC 5052, August 2007. Correction (FEC) Building Block", RFC 5052, August 2007.
[RFC5053] Luby, M., Shokrollahi, A., Watson, M., and T. Stockhammer, [RFC5053] Luby, M., Shokrollahi, A., Watson, M., and T. Stockhammer,
"Raptor Forward Error Correction Scheme for Object "Raptor Forward Error Correction Scheme for Object
Delivery", RFC 5053, October 2007. Delivery", RFC 5053, October 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4756] Li, A., "Forward Error Correction Grouping Semantics in [I-D.ietf-mmusic-rfc4756bis]
Session Description Protocol", RFC 4756, November 2006. Begen, A., "Forward Error Correction Grouping Semantics in
Session Description Protocol",
draft-ietf-mmusic-rfc4756bis-06 (work in progress),
February 2010.
[I-D.ietf-rmt-bb-fec-raptorq]
Luby, M., Shokrollahi, A., Watson, M., and T. Stockhammer,
"RaptorQ Forward Error Correction Scheme for Object
Delivery", draft-ietf-rmt-bb-fec-raptorq-01 (work in
progress), February 2010.
[dvbts] "ETSI TS 102 034 - Digital Video Broadcasting (DVB); [dvbts] "ETSI TS 102 034 - Digital Video Broadcasting (DVB);
Transport of MPEG-2 Based DVB Services over IP Based Transport of MPEG-2 Based DVB Services over IP Based
Networks", March 2005. Networks", March 2005.
[MBMSTS] 3GPP, "Multimedia Broadcast/Multicast Service (MBMS);
Protocols and codecs", 3GPP TS 26.346, April 2005.
Author's Address Author's Address
Mark Watson Mark Watson
Qualcomm, Inc. Qualcomm, Inc.
3165 Kifer Road 3165 Kifer Road
Santa Clara, CA 95051 Santa Clara, CA 95051
U.S.A. U.S.A.
Email: watson@qualcomm.com Email: watson@qualcomm.com
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