draft-ietf-fecframe-raptor-10.txt   draft-ietf-fecframe-raptor-11.txt 
FEC Framework M. Watson FEC Framework M. Watson
Internet-Draft Netflix Internet-Draft Netflix
Intended status: Standards Track T. Stockhammer Intended status: Standards Track T. Stockhammer
Expires: September 2, 2012 Nomor Research Expires: November 11, 2012 Nomor Research
M. Luby M. Luby
Qualcomm Incorporated Qualcomm Incorporated
March 1, 2012 May 10, 2012
Raptor FEC Schemes for FECFRAME Raptor FEC Schemes for FECFRAME
draft-ietf-fecframe-raptor-10 draft-ietf-fecframe-raptor-11
Abstract Abstract
This document describes Fully-Specified Forward Error Correction This document describes Fully-Specified Forward Error Correction
(FEC) Schemes for the Raptor and RaptorQ codes and their application (FEC) Schemes for the Raptor and RaptorQ codes and their application
to reliable delivery of media streams in the context of FEC to reliable delivery of media streams in the context of FEC
Framework. The Raptor and RaptorQ codes are systematic codes, where Framework. The Raptor and RaptorQ codes are systematic codes, where
a number of repair symbols are generated from a set of source symbols 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 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 symbols that are sent to the receiver(s) within a source flow. The
skipping to change at page 1, line 46 skipping to change at page 1, line 46
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This Internet-Draft will expire on September 2, 2012. This Internet-Draft will expire on November 11, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 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 Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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4. Definitions and Abbreviations . . . . . . . . . . . . . . . . 6 4. Definitions and Abbreviations . . . . . . . . . . . . . . . . 6
4.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7
5. General procedures for Raptor FEC Schemes . . . . . . . . . . 7 5. General procedures for Raptor FEC Schemes . . . . . . . . . . 7
6. Raptor FEC Schemes for arbitrary packet flows . . . . . . . . 9 6. Raptor FEC Schemes for arbitrary packet flows . . . . . . . . 9
6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 9
6.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 9 6.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 9
6.2.1. FEC Framework Configuration Information . . . . . . . 9 6.2.1. FEC Framework Configuration Information . . . . . . . 9
6.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 10 6.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 10
6.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 11 6.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 11
6.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 12 6.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 13
6.3.1. Source symbol construction . . . . . . . . . . . . . . 12 6.3.1. Source symbol construction . . . . . . . . . . . . . . 13
6.3.2. Repair packet construction . . . . . . . . . . . . . . 13 6.3.2. Repair packet construction . . . . . . . . . . . . . . 13
6.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 13 6.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 13
7. Optimised Raptor FEC Scheme for arbitrary packet flows . . . . 13 7. Optimised Raptor FEC Scheme for arbitrary packet flows . . . . 13
7.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 14 7.2. Formats and Codes . . . . . . . . . . . . . . . . . . . . 14
7.2.1. FEC Framework Configuration Information . . . . . . . 14 7.2.1. FEC Framework Configuration Information . . . . . . . 14
7.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 14 7.2.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 15
7.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 14 7.2.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 15
7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 14 7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 15
7.3.1. Source symbol construction . . . . . . . . . . . . . . 14 7.3.1. Source symbol construction . . . . . . . . . . . . . . 15
7.3.2. Repair packet construction . . . . . . . . . . . . . . 15 7.3.2. Repair packet construction . . . . . . . . . . . . . . 15
7.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 15 7.4. FEC Code Specification . . . . . . . . . . . . . . . . . . 15
8. Raptor FEC Scheme for a single sequenced flow . . . . . . . . 15 8. Raptor FEC Scheme for a single sequenced flow . . . . . . . . 16
8.1. Formats and codes . . . . . . . . . . . . . . . . . . . . 15 8.1. Formats and codes . . . . . . . . . . . . . . . . . . . . 16
8.1.1. FEC Framework Configuration Information . . . . . . . 15 8.1.1. FEC Framework Configuration Information . . . . . . . 16
8.1.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 16 8.1.2. Source FEC Payload ID . . . . . . . . . . . . . . . . 16
8.1.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 16 8.1.3. Repair FEC Payload ID . . . . . . . . . . . . . . . . 16
8.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 17 8.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 18
8.2.1. Source symbol construction . . . . . . . . . . . . . . 17 8.2.1. Source symbol construction . . . . . . . . . . . . . . 18
8.2.2. Derivation of Source FEC Packet Identification 8.2.2. Derivation of Source FEC Packet Identification
Information . . . . . . . . . . . . . . . . . . . . . 18 Information . . . . . . . . . . . . . . . . . . . . . 18
8.2.3. Repair packet construction . . . . . . . . . . . . . . 19 8.2.3. Repair packet construction . . . . . . . . . . . . . . 19
8.2.4. Procedures for RTP source flows . . . . . . . . . . . 19 8.2.4. Procedures for RTP source flows . . . . . . . . . . . 19
8.3. FEC Code Specification . . . . . . . . . . . . . . . . . . 19 8.3. FEC Code Specification . . . . . . . . . . . . . . . . . . 20
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20
10. Session Description Protocol (SDP) Signaling . . . . . . . . . 19 10. Session Description Protocol (SDP) Signaling . . . . . . . . . 20
11. Congestion Control Considerations . . . . . . . . . . . . . . 20 11. Congestion Control Considerations . . . . . . . . . . . . . . 21
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
12.1. Registration of FEC Scheme IDs . . . . . . . . . . . . . . 20 12.1. Registration of FEC Scheme IDs . . . . . . . . . . . . . . 21
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
14.1. Normative References . . . . . . . . . . . . . . . . . . . 22 14.1. Normative References . . . . . . . . . . . . . . . . . . . 22
14.2. Informative References . . . . . . . . . . . . . . . . . . 22 14.2. Informative References . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
The FEC Framework [RFC6363] describes a general framework for the use The Forward Error Correction (FEC) Framework [RFC6363] describes a
of Forward Error Correction in association with arbitrary packet general framework for the use of Forward Error Correction in
flows. Modeled after the FEC Building Block developed by the IETF association with arbitrary packet flows. Modeled after the FEC
Reliable Multicast Transport working group [RFC5052], the FEC Building Block developed by the IETF Reliable Multicast Transport
Framework defines the concept of FEC Schemes which provide specific working group [RFC5052], the FEC Framework defines the concept of FEC
Forward Error Correction schemes. This document describes six FEC Schemes which provide specific Forward Error Correction schemes.
Schemes which make use of the Raptor and RaptorQ FEC codes as defined This document describes six FEC Schemes which make use of the Raptor
in [RFC5053] and [RFC6330]. and RaptorQ FEC codes as defined in [RFC5053] and [RFC6330].
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, for example
example audio or video data. In general, the operation of the audio or video data. In general, the operation of the protection
protection mechanism is as follows: 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/RaptorQ protection operation on the o The sender applies the Raptor/RaptorQ protection operation on the
source symbols to generate the required number of repair symbols. source 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) and the source packets to the receiver(s). Per the FEC packet(s) and the source packets to the receiver(s). Per the FEC
Framework requirements, the sender MUST transmit the source and Framework requirements, the sender MUST transmit the source and
repair packets in different source and repair flows, or in the repair packets in different source and repair flows, or in the
case RTP transport is used for repair packets, in different RTP case Real-time Transport Protocol (RTP) transport is used for
streams. repair packets, in different RTP streams.
o At the receiver side, if all of the source packets are o 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 repair packets are discarded. However, if there are missing
source packets, the repair packets can be used to recover the source packets, the repair packets can be used to recover the
missing information. missing 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
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this document defines six FEC Schemes, two for the case of a single this document defines six FEC Schemes, two for the case of a single
sequenced flow and four for the case of arbitrary packet flows. sequenced flow and four 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:
o Section 5 defines general procedures applicable to the use of the o Section 5 defines general procedures applicable to the use of the
Raptor and RaptorQ codes in the context of the FEC Framework. Raptor and RaptorQ codes in the context of the FEC Framework.
o Section 6defines an FEC Scheme for the case of arbitrary source o Section 6 defines an FEC Scheme for the case of arbitrary source
flows and follows the format defined for FEC Schemes in [RFC6363]. flows and follows the format defined for FEC Schemes in [RFC6363].
When used with Raptor codes, this scheme is equivalent to that When used with Raptor codes, this scheme is equivalent to that
defined in "3GPP TS 26.346: Multimedia Broadcast/Multicast defined in "3GPP TS 26.346: Multimedia Broadcast/Multicast
Service (MBMS); Protocols and codecs" [MBMSTS]. Service (MBMS); Protocols and codecs" [MBMSTS].
o Section 7 defines an FEC Scheme similar to that defined in o Section 7 defines an FEC Scheme similar to that defined in
Section 6but with optimisations for the case where only limited Section 6 but with optimisations for the case where only limited
source block sizes are required. When used with Raptor codes, source block sizes are required. When used with Raptor codes,
this scheme is equivalent to that defined in "ETSI TS 102.034: this scheme is equivalent to that defined in "ETSI TS 102.034:
Digital Video Broadcasting (DVB); Transport of MPEG-2 Based DVB Digital Video Broadcasting (DVB); Transport of MPEG-2 Based DVB
Services over IP Based" Networks[dvbts] for arbitrary packet Services over IP Based Networks" [dvbts] for arbitrary packet
flows. flows.
o Section 8 defines an FEC Scheme for the case of a single flow o 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.
When used with Raptor codes, this scheme is equivalent to that When used with Raptor codes, this scheme is equivalent to that
defined in [dvbts] for the case 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
document are summarized in this section. document are summarized in this section.
4.1. Definitions 4.1. Definitions
This document uses definitions that apply to FEC Framework in general The FEC-specific terminology used in this document is defined in
as defined in [RFC6363]. In addition, this document uses the [RFC6363]. In this document, as in [RFC6363], the first letter of
following definitions: each FEC-specific is capitalized along with the new terms defined
here:
Symbol: A unit of data. Its size, in octets, is referred to as the Symbol: A unit of data. Its size, in octets, is referred to as the
symbol size. symbol size.
FEC Framework Configuration Information: Information that controls FEC Framework Configuration Information: Information that controls
the operation of the FEC Framework. Each FEC Framework instance the operation of the FEC Framework. Each FEC Framework instance
has its own configuration information. has its own configuration information.
4.2. Abbreviations 4.2. Abbreviations
This document uses abbreviations that apply to FEC Framework in This document uses abbreviations that apply to FEC Framework in
general as defined in [RFC6363]. In addition, this document uses the general as defined in [RFC6363]. In addition, this document uses the
following abbreviations following abbreviations
FSSI: FEC-Scheme-Specific Information. FSSI: FEC-Scheme-Specific Information.
SS-FSSI: Sender-Side FEC-Scheme-Specific Information. SS-FSSI: Sender-Side FEC-Scheme-Specific Information.
RS-FSSI: Receiver-Side FEC-Scheme-Specific Information. RS-FSSI: Receiver-Side FEC-Scheme-Specific Information.
ADU: Application Data Unit
ADUI: Application Data Unit Information. ADUI: Application Data Unit Information.
SPI: Source Packet Information. SPI: Source Packet Information.
MSBL Maximum Source Block Length MSBL: Maximum Source Block Length
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
and RaptorQ FEC Schemes, specifically the construction of source and RaptorQ FEC Schemes, specifically the construction of source
symbols from a set of source transport payloads. As described in symbols from a set of source transport payloads.
[RFC6363] for each Application Data Unit (ADU) in a source block, the
FEC Scheme is provided with: For any field defined in this document, the octets are ordered in
network byte order.
As described in [RFC6363] for each Application Data Unit (ADU) in a
source block, the FEC Scheme is provided with:
o A description of the source data flow with which the ADU is o A description of the source data flow with which the ADU is
associated and an integer identifier associated with that flow. associated and an integer identifier associated with that flow.
o The ADU itself. o The ADU itself.
o The length of the ADU. o The length of the ADU.
For each ADU, we define the Application Data Unit Information (ADUI) For each ADU, we define the Application Data Unit Information (ADUI)
as follows: as follows:
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[RFC6330] is used, as assigned by IANA. [RFC6330] is used, as assigned by IANA.
NOTE: To the RFC Editor: please change these XXX notations once NOTE: To the RFC Editor: please change these XXX notations once
assigned, and remove this NOTE. assigned, and remove this NOTE.
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:
MSBL Value range: A decimal non-negative integer less than 8192 for MSBL Value range: An non-negative integer less than 8192 for FEC
FEC Scheme XXX1 and less than 56403 for FEC Scheme XXX2, in units Scheme XXX1 and less than 56403 for FEC Scheme XXX2, in units of
of symbols symbols. The field type is unsigned integer.
Encoding Symbol Size Name: "T", Value range: A decimal non- Encoding Symbol Size Name: "T", Value range: A non-negative
negative integer less than 65536, in units of octets integer less than 65536, in units of octets. The field type is
unsigned integer.
Payload ID Format Name: "P", Value range: "A" or "B" Payload ID Format Name: "P", Value range: "A" or "B". The P bit
shall be set to zero to indicate Payload ID Format A or to one to
indicate Payload ID Format B.
An encoding format for The MSBL and Encoding Symbol Size is defined An encoding format for the MSBL and Encoding Symbol Size is defined
below. 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) | MSBL | | Symbol Size (T) | MSBL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P| Reserved | |P| Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 1: FEC Scheme Specific Information Figure 1: FEC Scheme Specific Information
The P bit shall be set to zero to indicate Payload ID Format A or to The P bit shall be set to zero to indicate Payload ID Format A or to
one to indicate Payload ID Format B. The last octet of FEC Scheme one to indicate Payload ID Format B. The last octet of FEC Scheme
Specific Information may be omitted indicating that Payload ID Format Specific Information SHOULD be omitted indicating that Payload ID
A is in use. The Payload ID Format identifier defines which of the Format A is in use. The Payload ID Format identifier defines which
Source FEC Payload ID and Repair FEC Payload ID formats defined below of the Source FEC Payload ID and Repair FEC Payload ID formats
shall be used. Payload ID Format B SHALL NOT be used for FEC Scheme defined below shall be used. Payload ID Format B SHALL NOT be used
XXX1. The two formats enable different use cases. Format A is for FEC Scheme XXX1. The two formats enable different use cases.
appropriate in case the stream has many typically smaller source Format A is appropriate in case the stream has many typically smaller
blocks and Format B is applicable if the stream has fewer large source blocks and Format B is applicable if the stream has fewer
source blocks each with many encoding symbols. large source blocks each with many encoding symbols.
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. Two formats are defined 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 for the Source FEC Payload ID, format A and format B. The format that
is used is signaled as part of the FEC Framework Configuration is used is signaled as part of the FEC Framework Configuration
Information. Information.
The Source FEC Payload ID for format A is provided in Figure 2. The Source FEC Payload ID for format A is provided in Figure 2.
.
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 - Format A 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): Identifier for the source
source block that the source data within the packet relates to. block that the source data within the packet relates. The field
type is unsigned integer.
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. The field type is unsigned
integer.
The Source FEC Payload ID for format B is provided in Figure 3. The Source FEC Payload ID for format B is provided in Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SBN | Encoding Symbol ID (ESI) | | SBN | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Source FEC Payload ID - Format B Figure 3: Source FEC Payload ID - Format B
Source Block Number (SBN), (8 bits): An integer identifier for the Source Block Number (SBN), (8 bits): Identifier for the source block
source block that the source data within the packet relates to. that the source data within the packet relates. The field type is
unsigned integer.
Encoding Symbol ID (ESI), (24 bits): The starting symbol index of Encoding Symbol ID (ESI), (24 bits): The starting symbol index of
the source packet in the source block. the source packet in the source block. The field type is unsigned
integer.
6.2.3. Repair FEC Payload ID 6.2.3. Repair FEC Payload ID
Two formats for the Repair FEC Payload ID, Format A and Format B are Two formats for the Repair FEC Payload ID, Format A and Format B are
defined below. defined below.
The Repair FEC Payload ID for format A is provided in Figure 4. The Repair FEC Payload ID for format A is provided in Figure 4.
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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Repair FEC Payload ID - Format A Figure 4: Repair FEC Payload ID - Format A
Source Block Number (SBN), (16 bits) An integer identifier for the Source Block Number (SBN), (16 bits) Identifier for the source block
source block that the repair symbols within the packet relate to. that the repair symbols within the packet relate. For format A,
For format A, it is of size 16 bits. it is of size 16 bits. The field type is unsigned integer.
Encoding Symbol ID (ESI), (16 bits) Integer identifier for the Encoding Symbol ID (ESI), (16 bits) Identifier for the encoding
encoding symbols within the packet. symbols within the packet. The field type is unsigned integer.
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. The field type is unsigned integer.
The Repair FEC Payload ID for format B is provided in Figure 5. The Repair FEC Payload ID for format B is provided in Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SBN | Encoding Symbol ID (ESI) | | SBN | Encoding Symbol ID (ESI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Block Length (SBL) | | Source Block Length (SBL) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Repair FEC Payload ID - Format B Figure 5: Repair FEC Payload ID - Format B
Source Block Number (SBN), (8 bits) An integer identifier for the Source Block Number (SBN), (8 bits) Identifier for the source block
source block that the repair symbols within the packet relate to. that the repair symbols within the packet relate. For format B,
For format B, it is of size 8 bits. it is of size 8 bits. The field type is unsigned integer.
Encoding Symbol ID (ESI), (24 bits) Integer identifier for the Encoding Symbol ID (ESI), (24 bits) Identifier for the encoding
encoding symbols within the packet. symbols within the packet. The field type is unsigned integer.
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. The field type is unsigned integer.
The interpretation of the Source Block Number, Encoding Symbol The interpretation of the Source Block Number, Encoding Symbol
Identifier and Source Block Length is defined by the FEC Code Identifier and Source Block Length is defined by the FEC Code
Specification in [RFC5053] for FEC Scheme XXX1 and [RFC6330] for FEC Specification in [RFC5053] for FEC Scheme XXX1 and [RFC6330] for FEC
Scheme XXX2. Scheme XXX2.
6.3. Procedures 6.3. Procedures
6.3.1. Source symbol construction 6.3.1. Source symbol construction
skipping to change at page 13, line 47 skipping to change at page 14, line 20
implementations. implementations.
In outline, the modifications are: In outline, the modifications are:
o All source blocks within a stream are encoded using the same o All source blocks within a stream are encoded using the same
source block size. Code shortening is used to encode blocks of source block size. Code shortening is used to encode blocks of
different sizes. This is achieved by padding every block to the different sizes. This is achieved by padding every block to the
required size using zero symbols before encoding. The zero required size using zero symbols before encoding. The zero
symbols are then discarded after decoding. The source block size symbols are then discarded after decoding. The source block size
to be used for a stream is signaled in the Maximum Source Block to be used for a stream is signaled in the Maximum Source Block
Length (MSBL) field of the scheme-specific information. This Length (MSBL) field of the scheme-specific information. The
allows for efficient parallel encoding of multiple streams. Note extended source block is constructed by adding zero or more
that the padding operation is equivalent to the padding operation padding symbols such that the total number of symbols, MSBL, is
in [RFC6330] with K' the specified MSBL and K the actual source one of the values listed in Section 7.4. Each padding symbol
block length K. consists of T octets where the value of each octet is zero. MSBL
MUST be selected as the smallest value of the possible values in
Section 7.4 that is greater than or equal to K.
o The possible choices of the MSBL for a stream is restricted to a o The possible choices of the MSBL for a stream is restricted to a
small specified set. This allows explicit operation sequences for small specified set. This allows explicit operation sequences for
encoding and decoding the restricted set of source block lengths encoding and decoding the restricted set of source block lengths
to be pre-calculated and embedded in software or hardware. to be pre-calculated and embedded in software or hardware.
When used with the Raptor codes specified in [RFC5053], this scheme When used with the Raptor codes specified in [RFC5053], this scheme
is equivalent to that specified in [dvbts] for arbitrary packet is equivalent to that specified in [dvbts] for arbitrary packet
flows. flows.
skipping to change at page 14, line 31 skipping to change at page 15, line 9
defined in this section is XXX3 when [RFC5053] is used and XXX4 when defined in this section is XXX3 when [RFC5053] is used and XXX4 when
[RFC6330] is used, as assigned by IANA. [RFC6330] is used, as assigned by IANA.
NOTE: To the RFC Editor: please change these XXX notations once NOTE: To the RFC Editor: please change these XXX notations once
assigned, and remove this NOTE. assigned, and remove this NOTE.
7.2.1.2. FEC Scheme specific information 7.2.1.2. FEC Scheme specific information
The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and
the same as specified for FEC Scheme XXX2 for FEC Scheme XXX4, as the same as specified for FEC Scheme XXX2 for FEC Scheme XXX4, as
specified in Section 6.2.2, except that the MSBL value is as defined specified in Section 6.2.1.2, except that the MSBL value is as
in Section 7.4. defined in Section 7.4.
7.2.2. Source FEC Payload ID 7.2.2. Source FEC Payload ID
The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and
the same as specified for FEC Scheme XXX2 for FEC Scheme XXX4, as the same as specified for FEC Scheme XXX2 for FEC Scheme XXX4, as
specified in Section 6.2.2. specified in Section 6.2.2.
7.2.3. Repair FEC Payload ID 7.2.3. Repair FEC Payload ID
The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and The same as specified for FEC Scheme XXX1 for FEC Scheme XXX3, and
skipping to change at page 15, line 21 skipping to change at page 15, line 46
Section 5.3.2 of [RFC5053] for FEC Scheme XXX3 and as specified in Section 5.3.2 of [RFC5053] for FEC Scheme XXX3 and as specified in
Section 4.4.2 of [RFC6330] for FEC Scheme XXX4, where K=SBL. The Section 4.4.2 of [RFC6330] for FEC Scheme XXX4, where K=SBL. The
value of SBL SHALL be at most the value of MSBL. value of SBL SHALL be at most the value of MSBL.
7.4. FEC Code Specification 7.4. FEC Code Specification
The FEC encoder defined in [RFC5053] SHALL be used for FEC Scheme The FEC encoder defined in [RFC5053] SHALL be used for FEC Scheme
XXX3 and the FEC encoder defined in [RFC6330] SHALL be used for FEC XXX3 and the FEC encoder defined in [RFC6330] SHALL be used for FEC
Scheme XXX4. The source symbols passed to the FEC encoder SHALL Scheme XXX4. The source symbols passed to the FEC encoder SHALL
consist of the source symbols constructed according to Section 6.3.1 consist of the source symbols constructed according to Section 6.3.1
extended with zero or more padding symbols such that the total number extended with zero or more padding symbols. The extension SHALL be
of symbols in the source block is equal to the MSBL signaled in the such that the total number of symbols in the source block is equal to
FEC Scheme Specific Information. Thus the value of the parameter K the MSBL signaled in the FEC Scheme Specific Information. Thus the
used by the FEC encoded is equal to the MSBL for all blocks of the value of the parameter K used by the FEC encoded is equal to the MSBL
stream. Padding symbols shall consist entirely of octets set to the for all blocks of the stream. Padding symbols shall consist entirely
value zero. The symbol size, T, to be used for source block of octets set to the value zero. The symbol size, T, to be used for
construction and the repair symbol construction is equal to the source block construction and the repair symbol construction is equal
Encoding Symbol Size signaled in the FEC Scheme Specific Information. to the Encoding Symbol Size signaled in the FEC Scheme Specific
Information.
For FEC Scheme XXX3, the parameter T SHALL be set such that the For FEC Scheme XXX3, the parameter T SHALL be set such that the
number of source symbols in any source block is at most 8192. The number of source symbols in any source block is at most 8192. The
MSBL parameter - and hence the number of symbols used in the FEC MSBL parameter, and hence the number of symbols used in the FEC
Encoding and Decoding operations - SHALL be set to one of the Encoding and Decoding operations, SHALL be set to one of the
following values: 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
For FEC Scheme XXX4, the parameter T SHALL be set such that the For FEC Scheme XXX4, the parameter T SHALL be set such that the
number of source symbols in any source block is less than 56403. The number of source symbols in any source block is less than 56403. The
MSBL parameter SHALL be set to one of the supported values for K' MSBL parameter SHALL be set to one of the supported values for K'
defined in Section 5.6 of [RFC6330]. defined in Section 5.6 of [RFC6330].
skipping to change at page 16, line 44 skipping to change at page 17, line 20
| Encoding Symbol ID | | Encoding Symbol ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Repair FEC Payload ID - Format A Figure 6: Repair FEC Payload ID - Format A
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. The field type is unsigned integer.
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. The field type is unsigned
integer.
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
is the ESI of the first repair symbol in the packet. is the ESI of the first repair symbol in the packet. The field
type is unsigned integer.
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 | Source Block Length | | Initial Sequence Number | Source Block Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encoding Symbol ID | | Encoding Symbol ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Repair FEC Payload ID - Format B Figure 7: 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. The field type is unsigned integer.
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. The field type is unsigned
integer.
Encoding Symbol ID (ESI) - 24 bits This field indicates which repair Encoding Symbol ID (ESI) - 24 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
is the ESI of the first repair symbol in the packet. is the ESI of the first repair symbol in the packet. The field
type is unsigned integer.
8.2. Procedures 8.2. Procedures
8.2.1. Source symbol construction 8.2.1. Source symbol construction
FEC Scheme XXX5 and FEC Scheme XXX6 use the procedures defined in FEC Scheme XXX5 and FEC Scheme XXX6 use the procedures defined in
Section 5 to construct a set of source symbols to which the FEC code Section 5 to construct a set of source symbols to which the FEC code
can be applied. can be applied.
During the construction of the source block: During the construction of the source block:
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8.3. FEC Code Specification 8.3. FEC Code Specification
The same as specified for FEC Scheme XXX3 for FEC Scheme XXX5, and The same as specified for FEC Scheme XXX3 for FEC Scheme XXX5, and
the same as specified for FEC Scheme XXX4 for FEC Scheme XXX6, as the same as specified for FEC Scheme XXX4 for FEC Scheme XXX6, as
specified in Section 7.4. specified in 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 [RFC6363]. No security vulnerabilities specific to this refer to [RFC6363]. Also consider relevant security considerations
document have been identified. in [RFC5053] and [RFC6330]. No security vulnerabilities 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 syntax follows This section provides an SDP [RFC4566] example. The syntax follows
the definition in [RFC6364] .Assume we have one source video stream the definition in [RFC6364] .Assume we have one source video stream
(mid:S1) and one FEC repair stream (mid:R1). We form one FEC group (mid:S1) and one FEC repair stream (mid:R1). We form one FEC group
with the "a=group:FEC-FR S1 R1" line. The source and repair streams with the "a=group:FEC-FR S1 R1" line. The source and repair streams
are sent to the same port on different multicast groups. The repair are sent to the same port on different multicast groups. The repair
window is set to 200 ms. window is set to 200 ms.
skipping to change at page 21, line 28 skipping to change at page 22, line 4
| XXX3 | Raptor FEC Scheme | Section 7 in this document using | | XXX3 | Raptor FEC Scheme | Section 7 in this document using |
| | Optimised for | Raptor [RFC5053]. | | | Optimised for | Raptor [RFC5053]. |
| | Arbitrary Packet | | | | Arbitrary Packet | |
| | Flows | | | | Flows | |
+----------+---------------------+----------------------------------+ +----------+---------------------+----------------------------------+
| XXX4 | RaptorQ FEC Scheme | XXX4 for the Optimised RaptorQ | | XXX4 | RaptorQ FEC Scheme | XXX4 for the Optimised RaptorQ |
| | Optimised for | FEC Scheme for Arbitrary Packet | | | Optimised for | FEC Scheme for Arbitrary Packet |
| | Arbitrary Packet | Flows (Section 7) using RaptorQ | | | Arbitrary Packet | Flows (Section 7) using RaptorQ |
| | Flows | [RFC6330]. | | | Flows | [RFC6330]. |
+----------+---------------------+----------------------------------+ +----------+---------------------+----------------------------------+
+----------+---------------------+----------------------------------+
| XXX5 | Raptor FEC Scheme | XXX5 for the Raptor FEC Scheme | | XXX5 | Raptor FEC Scheme | XXX5 for the Raptor FEC Scheme |
| | for a single | for a single sequence flow | | | for a single | for a single sequence flow |
| | sequence flow | (Section 8) using Raptor | | | sequence flow | (Section 8) using Raptor |
| | | [RFC5053]. | | | | [RFC5053]. |
+----------+---------------------+----------------------------------+ +----------+---------------------+----------------------------------+
| XXX6 | RaptorQ FEC Scheme | XXX6 for the RaptorQ FEC Scheme | | XXX6 | RaptorQ FEC Scheme | XXX6 for the RaptorQ FEC Scheme |
| | for a single | for a single sequence flow | | | for a single | for a single sequence flow |
| | sequence flow | (Section 8) using RaptorQ | | | sequence flow | (Section 8) using RaptorQ |
| | | [RFC6330]. | | | | [RFC6330]. |
+----------+---------------------+----------------------------------+ +----------+---------------------+----------------------------------+
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