draft-ietf-rmt-fec-bb-revised-01.txt		draft-ietf-rmt-fec-bb-revised-02.txt
	Reliable Multicast M. Watson		Reliable Multicast M. Watson
	Internet-Draft M. Luby		Internet-Draft M. Luby
	Expires: March 5, 2006 Digital Fountain		Expires: April 21, 2006 Digital Fountain
	L. Vicisano		L. Vicisano
	Cisco Systems, Inc.		Cisco Systems, Inc.
	September 1, 2005		October 18, 2005
	Forward Error Correction (FEC) Building Block		Forward Error Correction (FEC) Building Block
	draft-ietf-rmt-fec-bb-revised-01		draft-ietf-rmt-fec-bb-revised-02
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, each author represents that any		By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware		applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes		have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.		aware will be disclosed, in accordance with Section 6 of BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 36		skipping to change at page 1, line 36
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
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	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on March 5, 2006.		This Internet-Draft will expire on April 21, 2006.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2005).		Copyright (C) The Internet Society (2005).
	Abstract		Abstract
	This document describes how to use Forward Error Correction (FEC)		This document describes how to use Forward Error Correction (FEC)
	codes to efficiently provide and/or augment reliability for data		codes to efficiently provide and/or augment reliability for data
	transport. This document defines a framework for the definition of		transport. This document defines a framework for the definition of
	skipping to change at page 2, line 39		skipping to change at page 2, line 39
	6.2.4. Common FEC Object Transmission Information elements . 15		6.2.4. Common FEC Object Transmission Information elements . 15
	6.2.5. Scheme-specific FEC Object Transmission		6.2.5. Scheme-specific FEC Object Transmission
	Information element . . . . . . . . . . . . . . . . . 15		Information element . . . . . . . . . . . . . . . . . 15
	6.3. FEC Payload ID . . . . . . . . . . . . . . . . . . . . . . 16		6.3. FEC Payload ID . . . . . . . . . . . . . . . . . . . . . . 16
	7. FEC scheme specifications . . . . . . . . . . . . . . . . . . 17		7. FEC scheme specifications . . . . . . . . . . . . . . . . . . 17
	8. CDP specifications . . . . . . . . . . . . . . . . . . . . . . 20		8. CDP specifications . . . . . . . . . . . . . . . . . . . . . . 20
	9. Common algorithms . . . . . . . . . . . . . . . . . . . . . . 21		9. Common algorithms . . . . . . . . . . . . . . . . . . . . . . 21
	9.1. Block partitioning algorithm . . . . . . . . . . . . . . . 21		9.1. Block partitioning algorithm . . . . . . . . . . . . . . . 21
	9.1.1. First Step . . . . . . . . . . . . . . . . . . . . . . 21		9.1.1. First Step . . . . . . . . . . . . . . . . . . . . . . 21
	9.1.2. Second step . . . . . . . . . . . . . . . . . . . . . 22		9.1.2. Second step . . . . . . . . . . . . . . . . . . . . . 22
	10. Requirements from other building blocks . . . . . . . . . . . 24		10. Requirements from other building blocks . . . . . . . . . . . 23
	11. Security Considerations . . . . . . . . . . . . . . . . . . . 25		11. Security Considerations . . . . . . . . . . . . . . . . . . . 24
	12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26		12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
	12.1. Explicit IANA Assignment Guidelines . . . . . . . . . . . 26		12.1. Explicit IANA Assignment Guidelines . . . . . . . . . . . 25
	13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28		13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
	14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29		14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
	14.1. Normative References . . . . . . . . . . . . . . . . . . . 29		14.1. Normative References . . . . . . . . . . . . . . . . . . . 28
	14.2. Informative References . . . . . . . . . . . . . . . . . . 29		14.2. Informative References . . . . . . . . . . . . . . . . . . 28
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
	Intellectual Property and Copyright Statements . . . . . . . . . . 31		Intellectual Property and Copyright Statements . . . . . . . . . . 30
	1. Introduction		1. Introduction
	This document describes how to use Forward Error Correction (FEC)		This document describes how to use Forward Error Correction (FEC)
	codes to provide support for reliable delivery of content within the		codes to provide support for reliable delivery of content within the
	context of a Content Delivery Protocol (CDP). This document		context of a Content Delivery Protocol (CDP). This document
	describes a building block as defined in [10]. This document is a		describes a building block as defined in [10]. This document is a
	product of the IETF RMT WG and follows the general guidelines		product of the IETF RMT WG and follows the general guidelines
	provided in [8].		provided in [8].
	The purpose of this building block is to define a framework for		The purpose of this building block is to define a framework for
	forward error correction such that:		forward error correction such that:
	1. CDPs can be designed to operate with a range of different FEC		1. CDPs can be designed to operate with a range of different FEC
	codes/scheme, without needing to know details of the specific FEC		codes/schemes, without needing to know details of the specific
	code/scheme that may be used		FEC code/scheme that may be used
	2. FEC schemes can be designed to operate with a range of different		2. FEC schemes can be designed to operate with a range of different
	CDPs, without needing to know details of the specific CDPs		CDPs, without needing to know details of the specific CDPs
	Note that a 'CDP' in the context of this document may consist of		Note that a 'CDP' in the context of this document may consist of
	several distinct protocol mechanisms.		several distinct protocol mechanisms and may support any kind of
			application requiring reliable transport - for example object
			delivery and streaming applications.
	This document also provides detailed guidelines on how to write an		This document also provides detailed guidelines on how to write an
	RFC for an FEC scheme corresponding to a new FEC Encoding ID (for		RFC for an FEC scheme corresponding to a new FEC Encoding ID (for
	both Fully-Specified and Under-Specified FEC Schemes).		both Fully-Specified and Under-Specified FEC Schemes).
	2. Definitions/Abbreviations		2. Definitions/Abbreviations
	Object: An ordered sequence of bytes to be transferred by the		Object: An ordered sequence of bytes to be transferred by the
	transport protocol. For example, a file or stream.		transport protocol. For example, a file or stream.
	skipping to change at page 6, line 7		skipping to change at page 6, line 7
	FEC: Forward Error Correction		FEC: Forward Error Correction
	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 [1].		document are to be interpreted as described in [1].
	4. Rationale		4. Rationale
	FEC codes are a valuable basic component of any CDP that is to		An FEC code is a valuable basic component of any CDP that is to
	provide reliable delivery of an object. Using FEC codes is effective		provide reliable delivery of an object. Using FEC codes is effective
	in the context of IP multicast and reliable delivery because FEC		in the context of IP multicast and reliable delivery because FEC
	encoding symbols can be useful to all receivers for reconstructing an		encoding symbols can be useful to all receivers for reconstructing an
	object even when the receivers have received different encoding		object even when the receivers have received different encoding
	symbols. Furthermore, FEC codes can ameliorate or even eliminate the		symbols. Furthermore, FEC codes can ameliorate or even eliminate the
	need for feedback from receivers to senders to request retransmission		need for feedback from receivers to senders to request retransmission
	of lost packets.		of lost packets.
	Central to this document is the concept of an 'FEC Scheme'. An FEC		Central to this document is the concept of an 'FEC Scheme'. An FEC
	scheme defines ancilliary information and procedures which, combined		scheme defines ancilliary information and procedures which, combined
	skipping to change at page 11, line 34		skipping to change at page 11, line 34
	the FEC Object Transmission Information.		the FEC Object Transmission Information.
	The following requirements apply to all FEC schemes, whether Fully-		The following requirements apply to all FEC schemes, whether Fully-
	Specified or Under-Specified:		Specified or Under-Specified:
	o The type, semantics and an encoding format for the FEC Payload ID		o The type, semantics and an encoding format for the FEC Payload ID
	and the FEC Object Transmission Information MUST be defined.		and the FEC Object Transmission Information MUST be defined.
	o A value for the FEC Encoding ID MUST be reserved and associated		o A value for the FEC Encoding ID MUST be reserved and associated
	with the types, semantics and encoding format of the FEC Payload		with the types, semantics and encoding format of the FEC Payload
	ID and the the FEC Object Transmission Information.		ID and the FEC Object Transmission Information.
	The specification for an Under-Specified FEC Scheme MAY allocate a		The specification for an Under-Specified FEC Scheme MAY allocate a
	sub-field within the Scheme-specific FEC Object Transmission		sub-field within the Scheme-specific FEC Object Transmission
	Information element which is for instance-specific information. Each		Information element which is for instance-specific information. Each
	specific instance of the Under-Specified FEC Scheme may then use this		specific instance of the Under-Specified FEC Scheme may then use this
	field in an instance-specific way. The FEC scheme should define the		field in an instance-specific way. The FEC scheme should define the
	scheme-specific FEC Object Transmission Information element in such a		scheme-specific FEC Object Transmission Information element in such a
	way that receivers that do not support the received FEC Instance ID		way that receivers that do not support the received FEC Instance ID
	can still parse and interpret the scheme-specific FEC Object		can still parse and interpret the scheme-specific FEC Object
	Transmission Information element with the exception of the instance-		Transmission Information element with the exception of the instance-
	skipping to change at page 12, line 9		skipping to change at page 12, line 9
	An already defined Under-Specified FEC Scheme (i.e. FEC Encoding ID		An already defined Under-Specified FEC Scheme (i.e. FEC Encoding ID
	value) MUST be reused if the associated FEC Payload ID and FEC Object		value) MUST be reused if the associated FEC Payload ID and FEC Object
	Transmission Information have the required fields and encoding		Transmission Information have the required fields and encoding
	formats for a new Under-Specified FEC scheme instance.		formats for a new Under-Specified FEC scheme instance.
	An instance of an Under-Specified FEC scheme is fully identified by		An instance of an Under-Specified FEC scheme is fully identified by
	the tuple (FEC Encoding ID, FEC Instance ID). The tuple MUST		the tuple (FEC Encoding ID, FEC Instance ID). The tuple MUST
	identify a single scheme instance that has at least one		identify a single scheme instance that has at least one
	implementation. The party that owns this tuple MUST be able to		implementation. The party that owns this tuple MUST be able to
	provide information on how to obtain the the Under-Specified FEC		provide information on how to obtain the Under-Specified FEC scheme
	scheme instance identified by the tuple, e.g., a pointer to a		instance identified by the tuple, e.g., a pointer to a publicly
	publicly available reference-implementation or the name and contacts		available reference-implementation or the name and contacts of a
	of a company that sells it, either separately or embedded in another		company that sells it, either separately or embedded in another
	product.		product.
	This specification reserves the range 0-127 for the values of FEC		This specification reserves the range 0-127 for the values of FEC
	Encoding IDs for Fully-Specified FEC schemes and the range 128-255		Encoding IDs for Fully-Specified FEC schemes and the range 128-255
	for the values of Under-Specified FEC schemes.		for the values of Under-Specified FEC schemes.
	6.2. FEC Object Transmission Information		6.2. FEC Object Transmission Information
	The FEC Object Transmission Information contains information which is		The FEC Object Transmission Information contains information which is
	essential to the decoder in order to decode the encoded object. It		essential to the decoder in order to decode the encoded object. It
	skipping to change at page 12, line 44		skipping to change at page 12, line 44
	Object Transmission Information elements are determined and each		Object Transmission Information elements are determined and each
	CDP specifies how this information is encoded and reliably		CDP specifies how this information is encoded and reliably
	communicated to the receiver(s). The Mandatory FEC Object		communicated to the receiver(s). The Mandatory FEC Object
	Transmission Information includes the identification of the FEC		Transmission Information includes the identification of the FEC
	Scheme, which is needed by the receiver to determine whether it		Scheme, which is needed by the receiver to determine whether it
	supports the FEC Scheme.		supports the FEC Scheme.
	Common: These elements are defined in this specification and are		Common: These elements are defined in this specification and are
	optional to be used by an FEC scheme. Each FEC scheme specifies		optional to be used by an FEC scheme. Each FEC scheme specifies
	which of the Common FEC Object Transmission Information elements		which of the Common FEC Object Transmission Information elements
	it uses and how the values of these elements are determined. Each		it uses and how the values of these elements are determined.
	FEC scheme also specifies an encoding format for the information.
	Each CDP must specify at least one of the following:
	1. A means to reliably communicated the Common FEC Object		Scheme-specific: An FEC scheme may specify a single Scheme-specific
			FEC Object Transmission Information element. The FEC scheme
			specifies the type, semantics and encoding format of the Scheme-
			specific FEC Object Transmission Information element. The
			resulting byte-string is known as the "encoded Scheme-specific FEC
			Object Transmission Information". Each CDP specifies how the
			encoded Scheme-specific FEC Object Transmission is communicated
			reliably to the receiver(s) i.e. exactly where it shall be carried
			within packets of the CDP. Note that although from the point of
			view of this specification and of CDPs there is only a single
			Scheme-specific FEC Object Transmission Information element, the
			FEC scheme may specify this element to contain multiple distinct
			pieces of information.
			Each FEC scheme specifies an encoding format for the Common and
			Scheme-specific FEC Object Transmission Information. Each CDP must
			specify at least one of the following:
			1. A means to reliably communicate the Common FEC Object
	Transmission Information elements to the receiver(s) using the		Transmission Information elements to the receiver(s) using the
	encoding format defined by the FEC scheme.		encoding format defined by the FEC scheme.
	2. An alternative, CDP specific, encoding format for each of the		2. An alternative, CDP specific, encoding format for each of the
	Common FEC Object Transmission Information elements.		Common FEC Object Transmission Information elements.
	Scheme-specific: An FEC scheme may specify a single Scheme-specific
	FEC Object Transmission Information element. The FEC scheme
	specifies the type, semantics and encoding format of the Scheme-
	specific FEC Object Transmission Information element. The
	encoding format may assume that the receiver can determine the
	length of the Scheme-specific FEC Object Transmission Information
	element from information communicated outside that element. Each
	CDP specifies how the Scheme-specific FEC Object Transmission
	Element is communicated reliably to the receiver(s) i.e. exactly
	where it shall be carried within packets of the CDP. CDPs also
	specify how the length of the Scheme-specific FEC Object
	Transmission Information can be determined by the receiver. Note
	that although from the point of view of this specification and of
	CDPs there is only a single Scheme-specific FEC Object
	Transmission Information element, the FEC scheme may specify this
	element to contain multiple distinct pieces of information.
	The Mandatory and Common FEC Object Transmission Information elements		The Mandatory and Common FEC Object Transmission Information elements
	are defined in the sections below.		are defined in the sections below.
	6.2.1. Transport of FEC Object Transmission Information		6.2.1. Transport of FEC Object Transmission Information
	It is the responsibility of the CDP to reliably transport the FEC		It is the responsibility of the CDP to reliably transport the FEC
	Object Transmission Information to the receiver(s).		Object Transmission Information to the receiver(s).
	It is important to note that the encoding format of the Mandatory FEC		It is important to note that the encoding format of the Mandatory FEC
	Object Transmission Information elements (The FEC Encoding ID and FEC		Object Transmission Information elements (The FEC Encoding ID) is
	Instance ID) is defined by the CDP. This is so that the receiver can		defined by the CDP. This is so that the receiver can identify the
	identify the FEC Scheme to be used for interpreting the remaining FEC		FEC Scheme to be used for interpreting the remaining FEC Object
	Object Transmission Information elements. All CDPs must define		Transmission Information elements. All CDPs must define encoding
	encoding formats for all the Mandatory FEC Object Transmission		formats for the Mandatory FEC Object Transmission Information
	Information elements.		element.
	Common FEC Object Transmission Information elements can be		Common FEC Object Transmission Information elements can be
	transported in two different ways: (a) the FEC Scheme defines an		transported in two different ways: (a) the FEC Scheme defines an
	encoding format for each Common FEC Object Transmission Information		encoding format for the Common FEC Object Transmission Information
	element that it uses and the CDP transports it, or (b) the CDP		elements that it uses and the CDP transports this encoded data block,
	defines an encoding format and transports the information in this		or (b) the CDP defines an encoding format for each Common FEC Object
	format.		Transmission Information element and transports the information in
			this format.
	An FEC Scheme MUST define encoding formats for the Common FEC Object
	Transmission Information elements that it uses. A CDP MAY define
	encoding formats for the Common FEC Object Transmission Information
	elements. The CDP determines which way the Common FEC Object
	Transmission Information elements shall be transported, (a) or (b).
	Note that a CDP may provide support for one or both options.		An FEC Scheme MUST define an encoding format for the Common FEC
			Object Transmission Information elements that it uses. The resulting
			byte string is known as the "encoded Common FEC Object Transmission
			Information". A CDP MAY define individual encoding formats for each
			of the Common FEC Object Transmission Information elements. The CDP
			determines which way the Common FEC Object Transmission Information
			elements shall be transported, (a) or (b). Note that a CDP may
			provide support for one or both options.
	In the case that the CDP uses the encoding formats specified by the		In the case that the CDP uses the encoding format specified by the
	FEC scheme then it may simply concatenate the encoding formats		FEC scheme then it may simply concatenate the encoded Common FEC
	defined by the FEC scheme or it may carry each element in a seperate		Object Transmission Information and the encoded Scheme-specific FEC
	field or wrapper within the CDP. The FEC scheme must define the		Object Transmission Information or it may carry each in a seperate
	encoding formats of the Common FEC Object Transmission Information		field or wrapper within the CDP. In the former case, the
	elements that it uses in such a way that the length of each element		concatenated byte-string is known as the encoded FEC Object
	is either fixed or can be determined from the encoded data itself.		Transmission Information. The FEC scheme must define the encoding
			format for the Common FEC Object Transmission Information elements
			that it uses in such a way that the length of each element is either
			fixed or can be determined from the encoded data itself.
	The encoding format of the Scheme-specific FEC Object Transmission		The encoding format of the Scheme-specific FEC Object Transmission
	Information element is defined by the FEC scheme. CDPs specify only		Information element is defined by the FEC scheme. CDPs specify only
	how the resulting byte sequence is communicated. As with encoding		how the resulting byte sequence is communicated. As with the
	formats for the Common FEC Oject Transmission Information elements		encoding format for the Common FEC Oject Transmission Information
	the length of the Scheme-specific FEC Object Transmission Information		elements the length of the Scheme-specific FEC Object Transmission
	must either be fixed or it must be possible to determine the length		Information must either be fixed or it must be possible to determine
	from the encoded data itself.		the length from the encoded data itself.
	6.2.2. Opacity of FEC Object Transmission Information		6.2.2. Opacity of FEC Object Transmission Information
	The Scheme-specific FEC Object Transmission Information element is		The Scheme-specific FEC Object Transmission Information element is
	opaque to the CDP in the sense that inspecting the contents of this		opaque to the CDP in the sense that inspecting the contents of this
	element can only be done if FEC scheme-specific logic is included in		element can only be done if FEC scheme-specific logic is included in
	the CDP.		the CDP.
	The encoding formats defined by the FEC scheme for the Common FEC		The encoding formats defined by the FEC scheme for the Common FEC
	Object Transmission Information elements are also opaque to the CDP		Object Transmission Information elements are also opaque to the CDP
	in the same sense.		in the same sense.
	The encoding formats defined by the CDP for the Common FEC Object		The encoding formats defined by the CDP for the Common FEC Object
	Transmission Information elements are not opaque in this sense,		Transmission Information elements are not opaque in this sense,
	although it must be considered that different FEC Schemes may use		although it must be considered that different FEC Schemes may use
	different combinations of the Common FEC Object Transmission		different combinations of the Common FEC Object Transmission
	Information elements.		Information elements.
	6.2.3. Mandatory FEC Object Transmission Information elements		6.2.3. Mandatory FEC Object Transmission Information elements
	The Mandatory FEC Object Transmission Information elements are:		The Mandatory FEC Object Transmission Information element is:
	FEC Encoding ID: an integer between 0 and 255 inclusive identifying a		FEC Encoding ID: an integer between 0 and 255 inclusive identifying a
	specific FEC scheme (Fully-Specified or Under-Specified.)		specific FEC scheme (Fully-Specified or Under-Specified.)
	FEC Instance ID (if the FEC Encoding ID identifies an Under-Specified
	FEC scheme): an integer between 0 and 65535 inclusive identifying an
	instance of an Under-specifed FEC scheme
	6.2.4. Common FEC Object Transmission Information elements		6.2.4. Common FEC Object Transmission Information elements
	The Common FEC Object Transmission Information elements are described		The Common FEC Object Transmission Information elements are described
	below. Note that this specification does not provide complete		below. Note that with the exception of the FEC Instance ID, this
	definitions of these fields. Instead only aspects of the abstract		specification does not provide complete definitions of these fields.
	type are defined. The precise type and semantics are defined for		Instead only aspects of the abstract type are defined. The precise
	each FEC scheme in the FEC scheme specification.		type and semantics are defined for each FEC scheme in the FEC scheme
			specification.
			FEC Instance ID: an integer between 0 and 65535 inclusive identifying
			an instance of an Under-specifed FEC scheme
	Transfer-Length: a non-negative integer indicating the length of the		Transfer-Length: a non-negative integer indicating the length of the
	object in bytes		object in bytes
	Encoding-Symbol-Length: a non-negative integer indicating the length		Encoding-Symbol-Length: a non-negative integer indicating the length
	of each encoding symbol in bytes		of each encoding symbol in bytes
	Maximum-Source-Block-Length: a non-negative integer indicating the		Maximum-Source-Block-Length: a non-negative integer indicating the
	maximum number of source symbols in a source block		maximum number of source symbols in a source block
	Max-Number-of-Encoding-Symbols: a non-negative integer indicating the		Max-Number-of-Encoding-Symbols: a non-negative integer indicating the
	maximum number of encoding symbols (i.e. source plus repair		maximum number of encoding symbols (i.e. source plus repair
	symbols in the case of a systematic code)		symbols in the case of a systematic code)
			The FEC Instance ID MUST be used by all Under-specified FEC schemes
			and MUST NOT be used by Fully-specified FEC Schemes.
	FEC Schemes define the precise type of those of the above elements		FEC Schemes define the precise type of those of the above elements
	that they use and in particular may restrict the value range of each		that they use and in particular may restrict the value range of each
	element. FEC Schemes also define an encoding format for each of the		element. FEC Schemes also define an encoding format for the subset
	above elements that they use. CDPs may also provide an encoding		of the above elements that they use. CDPs may also provide an
	format for each element in which case this encoding format MUST be		encoding format for each element in which case this encoding format
	capable of representing values up to (2^^48)-1 in the case of the		MUST be capable of representing values up to (2^^16)-1 in the case of
	Transfer-Length and up to (2^^32)-1 for the other elements. CDPs may		the FEC Instance ID, (2^^48)-1 in the case of the Transfer-Length and
	additionally or alternatively provide a mechanism to transport these		up to (2^^32)-1 for the other elements. CDPs may additionally or
	elements encoded according to the encoding format defined by the FEC		alternatively provide a mechanism to transport the encoded Common FEC
	scheme. For example, FLUTE [8] specifies an XML-based encoding		Object Transmission information defined by the FEC scheme. For
	format for these elements, but can also transport FEC scheme-specific		example, FLUTE [8] specifies an XML-based encoding format for these
	encoding formats within the EXT-FTI header extension.		elements, but can also transport FEC scheme-specific encoding formats
			within the EXT-FTI LCT header extension.
	6.2.5. Scheme-specific FEC Object Transmission Information element		6.2.5. Scheme-specific FEC Object Transmission Information element
	The Scheme-specific FEC Object Transmission Information element may		The Scheme-specific FEC Object Transmission Information element may
	be used by an FEC Scheme to communicate information which is		be used by an FEC Scheme to communicate information which is
	essential to the decoder which cannot adequately be represented		essential to the decoder which cannot adequately be represented
	within the Mandatory or Common FEC Object Transmission Information		within the Mandatory or Common FEC Object Transmission Information
	elements.		elements.
	From the point of view of a CDP, the Scheme-specific FEC Object		From the point of view of a CDP, the Scheme-specific FEC Object
	Transmission Information element is an opaque, variable length,		Transmission Information element is an opaque, variable length, byte
	bitstring. The FEC Scheme defines the structure of this bitstring,		string. The FEC Scheme defines the structure of this byte string,
	which may contain multiple distinct elements.		which may contain multiple distinct elements.
	6.3. FEC Payload ID		6.3. FEC Payload ID
	The FEC Payload ID contains information which indicates to the FEC		The FEC Payload ID contains information which indicates to the FEC
	decoder the relationships between the encoding symbols carried by a		decoder the relationships between the encoding symbols carried by a
	particular packet and the FEC encoding transformation. For example		particular packet and the FEC encoding transformation. For example
	if the packet carries source symbols then the FEC Payload ID		if the packet carries source symbols then the FEC Payload ID
	indicates which source symbols of the object are carried by the		indicates which source symbols of the object are carried by the
	packet. If the packet carries repair symbols, then the FEC Payload		packet. If the packet carries repair symbols, then the FEC Payload
	skipping to change at page 19, line 9		skipping to change at page 19, line 9
	2. Formats and Codes		2. Formats and Codes
	2.1 FEC Payload ID(s) <define the type and format of one or two		2.1 FEC Payload ID(s) <define the type and format of one or two
	FEC Payload IDs>		FEC Payload IDs>
	2.2 FEC Object Transmission Information		2.2 FEC Object Transmission Information
	2.2.1 Mandatory <define the value of the FEC Encoding ID for		2.2.1 Mandatory <define the value of the FEC Encoding ID for
	this FEC scheme>		this FEC scheme>
	<in the case of Under-Specified FEC schemes, state the
	requirement for the FEC Instance ID to be part of the FEC
	Object Transmission Information>
	2.2.2 Common <describe which Common FEC Object Transmission		2.2.2 Common <describe which Common FEC Object Transmission
	Information elements are used by this FEC scheme, define		Information elements are used by this FEC scheme, define
	their value ranges and define an encoding format for them>		their value ranges and define an encoding format for them>
	2.2.3 Scheme-Specific <define the Scheme-specific FEC Object		2.2.3 Scheme-Specific <define the Scheme-specific FEC Object
	Transmission Information, including an encoding format, if		Transmission Information, including an encoding format, if
	required>		required>
	3. Procedures <describe any procedures which are specific to this		3. Procedures <describe any procedures which are specific to this
	FEC scheme, in particular derivation and interpretation of the		FEC scheme, in particular derivation and interpretation of the
	skipping to change at page 20, line 10		skipping to change at page 20, line 10
	Each FEC scheme MUST be specified independently of all other FEC		Each FEC scheme MUST be specified independently of all other FEC
	schemes; for example, in a separate specification or a completely		schemes; for example, in a separate specification or a completely
	independent section of larger specification.		independent section of larger specification.
	8. CDP specifications		8. CDP specifications
	A specification for a CDP that uses this building block MUST include		A specification for a CDP that uses this building block MUST include
	the following things:		the following things:
	1. Definitions of encoding formats for the Mandatory FEC Object		1. Definitions of an encoding formats for the Mandatory FEC Object
	Transmission Information elements.		Transmission Information element.
	2. A means to reliably communicate the Mandatory FEC Object		2. A means to reliably communicate the Mandatory FEC Object
	Transmission Information elements from sender to receiver(s)		Transmission Information element from sender to receiver(s) using
	using the encoding format defined in (1).		the encoding format defined in (1).
	3. Means to reliably communicate the Common FEC Object Transmission		3. Means to reliably communicate the Common FEC Object Transmission
	Information element from sender to receiver(s) using either or		Information element from sender to receiver(s) using either or
	both of (a) encoding formats defined by the FEC Scheme or (b)		both of (a) the encoding format defined by the FEC Scheme or (b)
	encoding formats defined by the CDP		encoding formats defined by the CDP
	4. A means to reliably communicate the Scheme-specific FEC Object		4. A means to reliably communicate the Scheme-specific FEC Object
	Transmission Information element from sender to receiver(s) using		Transmission Information element from sender to receiver(s) using
	the encoding format of the Scheme-specific FEC Object		the encoding format of the Scheme-specific FEC Object
	Transmission Information element defined by the FEC scheme.		Transmission Information element defined by the FEC scheme.
	5. A means to communicate the FEC Payload ID in association with a		5. A means to communicate the FEC Payload ID in association with a
	data packet. Note that the encoding format of the FEC Payload ID		data packet. Note that the encoding format of the FEC Payload ID
	is defined by the FEC Scheme.		is defined by the FEC Scheme.
	skipping to change at page 21, line 33		skipping to change at page 21, line 33
	blocks (N) are derived from the Object transfer length (L), Maximum		blocks (N) are derived from the Object transfer length (L), Maximum
	Source Block Length (B) and Symbol Length (E).		Source Block Length (B) and Symbol Length (E).
	In the second step, the partitioning of the object is derived from		In the second step, the partitioning of the object is derived from
	the number of source symbols (T) and the number of source blocks (N).		the number of source symbols (T) and the number of source blocks (N).
	The partitioning is defined in terms of a first number of source		The partitioning is defined in terms of a first number of source
	blocks (I), a second number of source blocks (N-I), the length of		blocks (I), a second number of source blocks (N-I), the length of
	each of the first source blocks (A_large) and the length of each of		each of the first source blocks (A_large) and the length of each of
	the second source blocks (A_small).		the second source blocks (A_small).
	This algorithm is identical to the one specified in Section 5.1.2.3
	of FLUTE [8]
	The following notation is used in the description below:		The following notation is used in the description below:
	ceil[x] denotes x rounded up to the nearest integer.		ceil[x] denotes x rounded up to the nearest integer.
	floor[x] denotes x rounded down to the nearest integer.		floor[x] denotes x rounded down to the nearest integer.
	9.1.1. First Step		9.1.1. First Step
	Input:		Input:
	skipping to change at page 22, line 51		skipping to change at page 22, line 48
	1. A_large = ceil[T/N]		1. A_large = ceil[T/N]
	2. A_small = floor[T/N]		2. A_small = floor[T/N]
	3. I = T - A_small * N		3. I = T - A_small * N
	Each of the first I source blocks then consists of A_large source		Each of the first I source blocks then consists of A_large source
	symbols, each source symbol is E bytes in length. Each of the		symbols, each source symbol is E bytes in length. Each of the
	remaining N-I source blocks consist of A_small source symbols, each		remaining N-I source blocks consist of A_small source symbols, each
	source symbol is E bytes in length except that the last source symbol		source symbol is E bytes in length except that the last source symbol
	of the last source block is L-(((L-1)/E) rounded down to the nearest		of the last source block is L-((L-1)/E) rounded down to the nearest
	integer)*E bytes in length.		integer)*E bytes in length.
	10. Requirements from other building blocks		10. Requirements from other building blocks
	The FEC building block does not provide any support for congestion		The FEC building block does not provide any support for congestion
	control. Any complete CDP MUST provide congestion control that		control. Any complete CDP MUST provide congestion control that
	conforms to [6], and thus this MUST be provided by another building		conforms to [6], and thus this MUST be provided by another building
	block when the FEC building block is used in a CDP.		block when the FEC building block is used in a CDP.
	There are no other specific requirements from other building blocks		There are no other specific requirements from other building blocks
End of changes. 30 change blocks.
	107 lines changed or deleted		110 lines changed or added
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