Internet DRAFT - draft-roca-nwcrg-fecframev2-problem-position
draft-roca-nwcrg-fecframev2-problem-position
IRTF Network Coding Research Group (NWCRG) V. Roca
Internet-Draft INRIA
Intended status: Informational November 14, 2016
Expires: May 18, 2017
FECFRAMEv2: Adding Sliding Encoding Window Capabilities to the FEC
Framework: Problem Position
draft-roca-nwcrg-fecframev2-problem-position-03
Abstract
The Forward Error Correction (FEC) Framework (or FECFRAME) (RFC 6363)
has been defined by the FECFRAME IETF WG to enable the use of FEC
Encoding with real-time flows in a flexible manner. The original
FECFRAME specification only considers the use of block FEC codes,
wherein the input flow(s) is(are) segmented into a sequence of blocks
and FEC encoding performed independently on a per-block basis. This
document discusses an extension of FECFRAME in order to enable a
sliding (potentially elastic) window encoding of the input flow(s),
using convolutional FEC codes for the erasure channel, as an
alternative to block FEC codes.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 18, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notations, Definitions and Abbreviations . . . . . . . . . . 4
2.1. Requirements Notation . . . . . . . . . . . . . . . . . . 4
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
3. Key features of FECFRAME . . . . . . . . . . . . . . . . . . 5
3.1. FECFRAME is more a shim layer than a protocol
instantiation . . . . . . . . . . . . . . . . . . . . . . 6
3.2. FECFRAME is highly flexible . . . . . . . . . . . . . . . 6
3.3. Details are in each FEC Scheme . . . . . . . . . . . . . 6
3.4. FECFRAME needs session-level description . . . . . . . . 7
4. Application of FECFRAME (RFC 6363) to network coding use-
cases: a discussion . . . . . . . . . . . . . . . . . . . . . 7
4.1. Block versus convolutional codes . . . . . . . . . . . . 7
4.2. End-to-end versus in-network re-coding . . . . . . . . . 8
4.3. Single versus multi-sources, intra versus inter-flows
coding . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4. Single versus multi-paths . . . . . . . . . . . . . . . . 8
5. Architectural considerations for FECFRAMEv2 . . . . . . . . . 9
5.1. FECFRAMEv2 in sliding encoding window mode . . . . . . . 9
5.2. ADU(I) to source symbol mapping . . . . . . . . . . . . . 11
5.3. Sliding encoding window management . . . . . . . . . . . 12
5.4. Encoding Symbol Identifiers (ESI) . . . . . . . . . . . . 13
5.5. Block and convolutional co-existence in a given
FECFRAMEv2 session . . . . . . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
The Forward Error Correction (FEC) Framework (or FECFRAME) [RFC6363],
produced by the FECFRAME IETF WG [fecframe-charter], describes a
framework for using Forward Error Correction (FEC) codes with
applications in public and private IP networks to provide protection
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against packet loss. The framework supports applying FEC to
arbitrary packet flows over unreliable transport and is primarily
intended for real-time, or streaming, media. This framework can be
used to define Content Delivery Protocols that provide FEC for
streaming media delivery or other packet flows. Content Delivery
Protocols defined using this framework can support any FEC scheme
(and associated FEC codes) that is compliant with various
requirements defined in [RFC6363]. Thus, Content Delivery Protocols
can be defined that are not specific to a particular FEC scheme, and
FEC schemes can be defined that are not specific to a particular
Content Delivery Protocol.
However, it is REQUIRED in [RFC6363] that the FEC scheme operate in a
block manner, i.e., the input flow(s) MUST be segmented into a
sequence of blocks, and FEC encoding (at a sender/coding node) and
decoding (at a receiver/decoding node) MUST be performed
independently on a per-block basis. This approach has a major impact
on coding and decoding delays when used with block FEC codes (e.g.,
[RFC6681], [RFC6816] or [RFC6865]) since encoding requires that all
the source symbols be known at the encoder. In case of continuous
input flow(s), even if source symbols can be sent immediately, repair
symbols are necessarily delayed by the block creation time, that
directly depends on the block size (i.e., the number of source
symbols in this block, k). This block creation time is also the
minimum decoding latency any receiver will experience in case of
erasures, since no repair symbol for the current block can be
received before. A good value for the block size is necessarily a
good balance between the minimum decoding latency at the receivers
(which must be in line with the most stringent real-time requirement
of the flow(s)) and the desired robustness in front of long erasure
bursts (which depends on the block size).
On the opposite, a convolutional code associated to a sliding
encoding window (of fixed size) or a sliding elastic encoding window
(of variable size) removes this minimum decoding delay, since repair
symbols can be generated and sent on-the-fly, at any time, from the
source symbols present in the current encoding window. Using a
sliding encoding window mode is therefore highly beneficial to real-
time flows, one of the primary targets of FECFRAME.
The present document introduces the FECFRAME framework specificities,
its limits, and options to extend it to sliding (optionally elastic)
encoding windows and convolutional codes.
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2. Notations, Definitions and Abbreviations
2.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2.2. Definitions
This document uses the following definitions, that are mostly
inspired from [RFC5052], [RFC6363] and [nc-taxonomy-id].
Packet Erasure Channel:
a communication path where packets are either dropped (e.g., by a
congested router or because the number of transmission errors
exceeds the correction capabilities of the physical layer codes)
or received. When a packet is received, it is assumed that this
packet is not corrupted
Systematic Code:
code in which the Source Symbols are part of the Output Symbols
Input Symbol:
a unit of data that is provided as an input to the coding process,
in a given coding node. It may be a source symbol or an already
encoded repair symbol if in-network re-coding is considered
Output Symbol:
a unit of data that is produced as an output of the coding
process, in a given coding node
Application Data Unit (ADU):
The unit of source data provided as payload to the transport
layer. Depending on the use-case, an ADU may use an RTP
encapsulation.
ADU Information (ADUI):
a unit of data constituted by the ADU and the associated Flow ID,
Length and Padding fields (Section 5.2).
Source Symbol:
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an original unit of data, before any coding process is applied.
Source symbols are the result of the fragmentation of ADUIs.
Repair Symbol:
an Output Symbol that is not a Source Symbol.
FEC Source Packet:
At a sender (respectively, at a receiver) a payload submitted to
(respectively, received from) the transport protocol containing an
ADU along with an Explicit Source FEC Payload ID (if present).
FEC Repair Packet:
At a sender (respectively, at a receiver) a payload submitted to
(respectively, received from) the transport protocol containing a
repair symbol (or several repair symbols with certain FEC Schemes)
along with a Repair FEC Payload ID (and possibly an RTP header in
some cases).
(Source) ADU Flow:
A sequence of ADUs associated with a transport-layer flow
identifier (such as the standard 5-tuple {Source IP address,
source port, destination IP address, destination port, transport
protocol}). Depending on the use-case, several ADU flows may be
protected together by the FECFRAME framework.
FEC Source Packet Flow:
A sequence of FEC Source Packets.
FEC Repair Packet Flow:
A sequence of FEC Repair Packets.
FEC Framework Configuration Information (FFCI):
Information which controls the operation of the FEC Framework.
The FFCI enables the synchronization of the FECFRAME sender and
receiver instances.
3. Key features of FECFRAME
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3.1. FECFRAME is more a shim layer than a protocol instantiation
FECFRAME is not a full featured Protocol Instantiation (unlike ALC
[RFC5775] and NORM [RFC5740] for instance). It is more a shim layer,
or more precisely a framework for using FEC inside existing transport
protocols. For instance when FECFRAME is used end-to-end inside a
single RTP/UDP stream (the simplest use-case), RTP [RFC3550] and UDP
are the transport protocols and FECFRAME is a functional component
that performs FEC encoding/decoding and generates RTP compliant
repair packets. Even if specific headers are defined for the
associated FEC Scheme, FECFRAME is not a full featured transport
protocol.
3.2. FECFRAME is highly flexible
FECFRAME is highly flexible in the way it can be used. In particular
FECFRAME:
o can protect a single RTP flow [RFC3550], repair packets being
themselves RTP packets, possibly multiplexed in the same UDP
connection but using a different Payload Type (PT) to distinguish
them from source packets. This is particularly useful if backward
compatibility is mandatory: non-FECFRAME aware receivers simply
drop packets with unknown PT. However this should be regarded as
a particular case;
o can protect a single source flow that does NOT use RTP, where
repair packets are NOT RTP packets either;
o can protect several source flows, from the same source or from
several sources, some of them being RTP flows but not necessarily
the other ones;
o can generate a single repair flow or multiple repair flows;
o can be used with any upper protocols (RTP or any other protocol)
and transport protocols (e.g., UDP, DCCP) if this latter preserves
datagram boundaries;
o can be used with unicast or multicast/broadcast transmissions;
3.3. Details are in each FEC Scheme
In the FECFRAME architecture, most technical details are in the FEC
Scheme. In particular a FEC Scheme defines:
o FEC code specifications and associated FEC Encoding ID;
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o the way source symbols are created from the data units coming from
the application(s), called Application Data Units (ADU);
o signaling for FEC Source Packets (optional), called Source FEC
Payload ID;
o signaling for FEC Repair Packets (mandatory), called Repair FEC
Payload ID;
3.4. FECFRAME needs session-level description
FECFRAME works in conjunction with SDP (or a similar protocol) to
specify high level per FECFRAME Instance (i.e., per-session)
signaling [RFC6364]. This information, called FEC Framework
Configuration Information [RFC6363], describes:
o the incoming flows (content description and flow identification);
o the outgoing flows, for source and repair packets;
o what FEC Scheme is used, identified via the FEC Encoding ID;
o and the FEC Scheme specific parameters.
In practice, the FEC Scheme is valid for the whole FECFRAME Instance
duration, since no update mechanism has been defined to carry a new
SDP session description reliably and in real-time to all the
potential receivers. This is different from ALC or NORM where the
FEC Scheme selection is made on a per-object manner (rather than per-
session).
4. Application of FECFRAME (RFC 6363) to network coding use-cases: a
discussion
The FECFRAME framework has a certain number of features and
restrictions. We discuss each of them below, at the light of the
use-cases identified for Network Coding.
4.1. Block versus convolutional codes
FECFRAME, as described in [RFC6363], MUST be associated to block FEC
codes. For instance ([RFC6363], section 5.1) says:
"1. Construction of a source block from ADUs. The FEC code will
be applied to this source block to produce the repair payloads."
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Therefore the input flow(s) is (resp. are) segmented into a sequence
of blocks, FEC encoding being performed independently on a per-block
basis.
However this is not a fundamental limitation, in the sense that the
same FECFRAME architecture can be used with sliding (potentially
elastic) encoding windows, associated with convolutional codes. To
that purpose it is sufficient:
o to update [RFC6363] adding the support of sliding (potentially
elastic) encoding windows along with the source block approach;
o to specify dedicated FEC Schemes, working with convolutional FEC
codes for the erasure channel. All the details of the codes, the
required signaling, the management of the sliding encoding window
and creation of source symbols will be defined in these FEC
Schemes.
4.2. End-to-end versus in-network re-coding
The FECFRAME architecture, as specified in [RFC6363], MUST feature a
single encoding node and a single decoding node. These nodes may be
the source and destination nodes, or may be middle-boxes, or any
combination.
The question of having multiple in-network re-coding operations is
not considered in [RFC6363]. The question whether this is feasible
and appropriate, given the typical FECFRAME use-cases, is an open
question that remains to be discussed.
4.3. Single versus multi-sources, intra versus inter-flows coding
FECFRAME, as specified in [RFC6363], can globally protect several
flows that can originate either from a single source or from multiple
sources. This also means that FECFRAME can perform both intra-flow
coding or inter-flows coding. The only requirement is that those
flows be identified and signaled to the FECFRAME encoder and decoder
via the FEC Framework Configuration Information (e.g., it can be
detailed in the SDP description).
From this point of view, FECFRAME is already in line with advanced
network-coding use-cases.
4.4. Single versus multi-paths
FECFRAME, as specified in [RFC6363], does not specify nor restrict
how the FEC Source Packet Flow(s) and FEC Repair Packet Flow(s) are
to be transmitted: whether they go through the same path (e.g., when
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they are sent to the same UDP connection) or through multiple paths
is irrelevant to FECFRAME since it is an operational and management
aspect. However, it is anticipated that when several repair flows
are generated, offering different protections levels (e.g., through
different code-rates), these repair flows will often use different
paths, to better accommodate receiver heterogeneity.
From this point of view, FECFRAME is already in line with advanced
network-coding use-cases.
5. Architectural considerations for FECFRAMEv2
Several architectural considerations are now discussed for version 2
of FECFRAME. We assume hereafter that FECFRAMEv2 follows the initial
spirit of FECFRAME, i.e., is only applied in end-to-end (see
Section 4.2). From what follows we show that adding sliding encoding
window support to FECFRAMEv2 is simple and can coexist with legacy
FECFRAME flows. Extending FECFRAMEv2 to other situations, e.g., with
in-network re-coding, is not considered in this document.
5.1. FECFRAMEv2 in sliding encoding window mode
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+----------------------+
| Application |
+----------------------+
|
| (1) Application Data Units (ADUs)
v
+----------------------+ +----------------+
| FEC Framework v2 | | |
| |-------------------------->| FEC Scheme |
|(2) Update of sliding | (3) Source Symbols of | |
| encoding window | the sliding window | |
| |<--------------------------| |
| | (4) Explicit Source | |
|(7) Construct FEC | FEC Payload ID(s) |(5) FEC Encoding|
| source and repair |<--------------------------| (optional) |
| packet(s) | (6) Repair FEC Payload ID | |
+----------------------+ + Repair symbol(s) +----------------+
|
| (8) FEC source packets and FEC repair packets
v
+----------------------+
| Transport Layer |
| (e.g., UDP) |
+----------------------+
Figure 1: Architecture of FECFRAMEv2 in sliding encoding window mode,
at a sender/coding node.
Figure 1 (adapted from [RFC6865]) illustrates the general
architecture of FECFRAMEv2 when working in sliding encoding window
mode. The difference with respect to the [RFC6363] architecture lies
in steps 2 to 6. Instead of creating a source block, composed of a
certain number of ADUs plus their associated flow/length/padding
information (see for instance [RFC6865]), FECFRAMEv2 in sliding
encoding window mode continuously updates this window (step 2) and
communicates the set of symbols to the FEC Scheme (step 3). This
latter then returns the Explicit Source FEC Payload ID(s) (step 4) so
that the new symbol(s) can be sent immediately. When FECFRAMEv2
needs to send one or several FEC repair packets (this is determined
by the desired target code rate), it asks the FEC Scheme to create
one or several repair symbols (step 5) along with their Repair FEC
Payload ID (step 6). The associated FEC Repair Packets are then sent
(steps 7 and 8).
When FECFRAMEv2 works with a block FEC Scheme, Figure 2 and Figure 3
of [RFC6363] remain valid, without any change.
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5.2. ADU(I) to source symbol mapping
Let us now detail the ADU to source symbol mapping. As in FECFRAME,
each ADU is first prepended with its {flow ID, length} information
(respectively the F and L fields of Figure 2) and potentially zero
padded to align to a multiple of the target symbol length ("0
padding" field of Figure 2). This augmented ADU is called ADUI.
ADUIs are then mapped to source symbols. Since incoming ADUs can
have largely varying sizes, it makes sense to use a symbol size
significantly lower than the PMTU (as in [MBMS], section 8.2.2.7)
which means that large ADUIs will be segmented into several source
symbols while small ADUIs may fit into a single or low number of
symbols. This has the advantage of limiting transmission overhead if
at the same time the FEC Scheme enables the transmission of several
repair symbols in the same FEC Repair Packet. However one may also
choose to associate a symbol size equal to the maximum ADUI size of
the current block, in case of a block FEC Scheme, as in [RFC6816] or
[RFC6865], in order to always have a one-to-one mapping between ADUIs
and source symbols.
The block versus sliding window mode does have an impact on the
strategy chosen. More precisely:
o FECFRAMEv2 in sliding window mode MUST use a fixed symbol size,
indicated in the FEC Framework Configuration Information (FFCI).
o FECFRAMEv2 in block mode and FECFRAME MAY use a dynamic symbol
size, chosen on a per-block basis, or MAY use a fixed symbol size,
indicated in the FEC Framework Configuration Information (FFCI).
In any case it is recommended that the symbol size be small enough
with respect to the PMTU.
FEC code related considerations can impact the choice of a symbol
size (assuming they are of fixed size). This is out of the scope of
this document.
Figure 2 illustrates the creation of the ADUIs from incoming ADUs and
the mapping to source symbols in case of small, fixed size symbols.
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Symbol Length Symbol Length
<-----------------------><----------------------->
+----+----+-------------------------+------------+
|F[i]|L[i]|ADU[i] | 0 padding | => symbols j, j+1
+----+----+-------+-----+-----------+------------+
|Fi+1|Li+1|ADUi+1 | 0 | => symbol j+2
+----+----+-------+---+-+
|Fi+2|Li+2|ADUi+2 |0| => symbols j+3
+----+----+-----------+-+------+-----------------+
|Fi+3|Li+3|ADUi+3 | 0 padding | => symbols j+4, j+5
+----+----+--------------------+-----------------+
Figure 2: ADUI and source symbols, case of small symbol sizes, for
either FECFRAME or FECFRAMEv2.
5.3. Sliding encoding window management
Let us now detail the sliding window update process at a sender. Two
kinds of limitations exist that impact the sliding window management:
o at the FEC Scheme level: this latter can have internal or
practical limitations (e.g., for complexity reasons) that limit
the number of source symbols in the encoding window;
o at the FECFRAMEv2 instance level: the source flows can have real-
time constraints that limit the number of source symbols in the
encoding window;
The most stringent limitation defines the maximum window size in
terms of either number of source symbols or number of ADUs (depending
on the relationship between them, see Section 5.2, they can be equal
or not).
Source symbols are added to the sliding encoding window as ADUs
arrive.
Source symbols (and the corresponding ADUs) are removed from the
sliding encoding window:
o after a certain delay, for situations where the sliding encoding
window is managed on a time basis. The motivation is that an old
ADU of a real-time flow becomes useless after a certain delay.
The ADU retention delay in the sliding encoding window is
therefore initialized according to the real-time features of
incoming flow(s);
o once the sliding encoding window has reached its maximum size,
when there is an upper limit to the sliding encoding window size;
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o when the sliding encoding window is of fixed size, the oldest
symbol is removed each time a new symbol is added;
o if the sender knows that a particular ADU has been correctly
received by the receiver(s), the corresponding source symbol(s)
is(are) removed. Of course this mechanism requires that an
acknowledgement mechanism be setup to inform the FECFRAMEv2 sender
of good ADU reception, which is out of the scope of FECFRAMEv2.
5.4. Encoding Symbol Identifiers (ESI)
Any **source** symbol of a flow MUST be uniquely identified during
the full duration where this symbol is useful.
Depending on the FEC Scheme being used, a **repair** symbol of a flow
may or not need to be uniquely identified during the full duration
where this symbol is useful. For instance, being able to identify a
repair symbol is OPTIONAL with Random Linear Codes (RLC) since the
coding window content and associated coding vector are communicated
in the Repair FEC Payload ID and nothing else is needed to process
this repair symbol. But being able to identify a repair symbol is
REQUIRED with FEC Schemes that use this symbol identifier during the
encoding and decoding processes (this is the case for instance with
any block FEC code and some of the convolutional FEC codes).
In block mode, the encoding symbols are uniquely identified both by
their Source Block Number (SBN) and Encoding Symbol ID (ESI), the
first k ESI values identifying source symbols and the remaining n-k
ESI values the repair symbols [RFC5052]. In sliding encoding window
mode, the situation is totally different:
o since there is no block, there is no SBN;
o since there is no block, the ESI space that identifies source
symbols is linear, each source symbol having an ESI that is 1
greater than the previous source symbol, except when a wrap-around
to zero occurs after reaching the maximum ESI value permitted by
the ESI field size (see below);
o an ESI space dedicated to repair symbols is used when the FEC
Scheme requires repair symbols to be identified. This ESI space
is logically different from the ESI space used for source symbols.
Therefore the same ESI value identifies different symbols
depending on whether we are considering a FEC source packet or FEC
repair packet. This is the context (e.g., the transport
identifiers like the destination UDP port number) that enables a
FECFRAME receiver to distinguish between source and repair
symbols, not the ESI value;
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Since the ESI space is limited by the header/trailer ESI field size
to b bits (as specified by the FEC Scheme), wrap-around to zero is
unavoidable with long FECFRAMEv2 sessions. This has two
consequences:
o the maximum sliding encoding window size MUST be smaller than
2^^b, and in practice be significantly smaller;
o if the network may significantly delay packets, there is a risk of
confusion if an ESI wrap-around takes place in the meantime, since
the delayed symbol may be misinterpreted as a fresh symbol. A
security margin is therefore needed that consists in having a "b"
value sufficiently large to avoid such confusions. What security
margin to consider is a deployment decision that also depends on
the various flow transmission bitrates. Note that a timestamp
information carried in FEC Source Packets may help identifying
delayed packets. However this is not a generic mechanism since
ADU flows are not required to use RTP framing.
5.5. Block and convolutional co-existence in a given FECFRAMEv2 session
When two (or more) FEC Repair Packet Flows are used in a given
FECFRAME session, it is possible to have both a block FEC Scheme on
one flow and a convolutional FEC Scheme on the other flow, both of
them protecting the same ADU flow(s). This can be useful in order to
preserve backward compatibility, legacy receivers joining the FEC
Repair Packet Flow corresponding to the block FEC Scheme and ignoring
the other flow.
The SDP description associated to this FECFRAMEv2 session indicates
if a FEC Repair Packet flow works in block mode or sliding encoding
window mode. This is done through the FEC Encoding ID communicated
via the "a=fec-repair-flow: encoding-id=0; ..." attribute [RFC6364]
(or "a=FEC-declaration:VALUE encoding-id=VALUE" attribute in case of
[MBMS]). Then, from this FEC Encoding ID, the FECFRAME receiver can
easily deduce if the FEC Scheme corresponds to a block or a
convolutional FEC code.
6. Security Considerations
Adding the new sliding window mode to FECFRAMEv2 (what this document
is about) in addition to the block mode of FECFRAME, while keeping
the end-to-end approach of FECFRAME, does not fundamentally change
the situation from a security point of view. Therefore all the
security considerations detailed in [RFC6363] also apply to
FECFRAMEv2. More precisely:
o the problem statement, section 9.1 of [RFC6363];
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o the attacks against the data flows, section 9.2 of [RFC6363];
o the attacks against the FEC parameters, section 9.3 of [RFC6363];
o the discussion related to the FEC protection of several source
flows, section 9.4 of [RFC6363];
o and the baseline secure FEC Framework operation, section 9.5 of
[RFC6363];
all apply to FECFRAMEv2, regardless of whether it follows a block or
sliding window mode. Security considerations specific to a FEC
Scheme, if any, will have to be discussed in the associated FEC
Scheme document.
7. Privacy Considerations
Adding the new sliding window mode to FECFRAMEv2 (what this document
is about), in addition to the block mode of FECFRAME, does not change
the situation from a privacy point of view. Those considerations
will be discussed in an update of [RFC6363].
8. IANA Considerations
N/A
9. Acknowledgments
The author wants to thank Morten V. Pedersen for his comments to
this document.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC5052] Watson, M., Luby, M., and L. Vicisano, "Forward Error
Correction (FEC) Building Block", RFC 5052,
DOI 10.17487/RFC5052, August 2007,
<http://www.rfc-editor.org/info/rfc5052>.
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[RFC6363] Watson, M., Begen, A., and V. Roca, "Forward Error
Correction (FEC) Framework", RFC 6363,
DOI 10.17487/RFC6363, October 2011,
<http://www.rfc-editor.org/info/rfc6363>.
[RFC6364] Begen, A., "Session Description Protocol Elements for the
Forward Error Correction (FEC) Framework", RFC 6364,
DOI 10.17487/RFC6364, October 2011,
<http://www.rfc-editor.org/info/rfc6364>.
10.2. Informative References
[fecframe-charter]
FECFRAME WG, IETF., "FEC Framework (fecframe) charter",
URL: http://www.ietf.org/wg/concluded/fecframe.html, March
2013.
[MBMS] 3rd Generation Partnership Project (3GPP) SA4 Working
Group, , "Multimedia Broadcast/Multicast Service (MBMS):
Protocols and codecs", 3GPP TS
26.346 http://www.3gpp.org/DynaReport/26346.htm, March
2016.
[nc-taxonomy-id]
Firoiu, V., Adamson, B., Roca, V., Adjih, C., Bilbao, J.,
Fitzek, F., Masucci, A., and M. Montpetit, "Network Coding
Taxonomy", draft-irtf-nwcrg-network-coding-taxonomy-00
(work in progress), November 2014.
[RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker,
"NACK-Oriented Reliable Multicast (NORM) Transport
Protocol", RFC 5740, DOI 10.17487/RFC5740, November 2009,
<http://www.rfc-editor.org/info/rfc5740>.
[RFC5775] Luby, M., Watson, M., and L. Vicisano, "Asynchronous
Layered Coding (ALC) Protocol Instantiation", RFC 5775,
DOI 10.17487/RFC5775, April 2010,
<http://www.rfc-editor.org/info/rfc5775>.
[RFC6681] Watson, M., Stockhammer, T., and M. Luby, "Raptor Forward
Error Correction (FEC) Schemes for FECFRAME", RFC 6681,
DOI 10.17487/RFC6681, August 2012,
<http://www.rfc-editor.org/info/rfc6681>.
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[RFC6816] Roca, V., Cunche, M., and J. Lacan, "Simple Low-Density
Parity Check (LDPC) Staircase Forward Error Correction
(FEC) Scheme for FECFRAME", RFC 6816,
DOI 10.17487/RFC6816, December 2012,
<http://www.rfc-editor.org/info/rfc6816>.
[RFC6865] Roca, V., Cunche, M., Lacan, J., Bouabdallah, A., and K.
Matsuzono, "Simple Reed-Solomon Forward Error Correction
(FEC) Scheme for FECFRAME", RFC 6865,
DOI 10.17487/RFC6865, February 2013,
<http://www.rfc-editor.org/info/rfc6865>.
Author's Address
Vincent Roca
INRIA
655, av. de l'Europe
Inovallee; Montbonnot
ST ISMIER cedex 38334
France
Email: vincent.roca@inria.fr
URI: http://privatics.inrialpes.fr/people/roca/
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