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nwcrg                                                           I. Swett
Internet-Draft                                                    Google
Intended status: Informational                              M. Montpetit
Expires: September 4, 2018                                Triangle Video
                                                                 V. Roca
                                                                   INRIA
                                                           March 3, 2018


                            Coding for QUIC
                  draft-swett-nwcrg-coding-for-quic-00

Abstract

   This document introduces means of integrating loss recovery coding in
   the proposed QUIC transport protocol.  While no specific code is
   specified, the document defines how to integrate recent coding
   research to recover packets lost in QUIC sessions.  This research
   targets the codes themselves as well as how to use them in real world
   protocols.  Loss recover should improve the QUIC performance in
   sessions impacted by loss.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 4, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Design Considerations . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Framing . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Coding Symbol . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Negotiation . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     3.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Appendix: Reference Algorithms . . . . . . . . . . .   5
   Appendix B.  Appendix: Participating Middleboxes  . . . . . . . .   5
   Appendix C.  Appendix: APIS . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   QUIC is a new transport that wants to improve network performance by
   enabling out of order delivery, partial reliability, and methods of
   recovery besides retransmission while also improving security.  This
   document specifies a design to enable error correcting codes to be
   used to recover lost data in QUIC.  Error correcting codes have the
   ability to recover packet losses in less than 1 round trip at the
   cost of more total data transmission and decoding delay.  The design
   does not specify a code but allows to negotiate it hence assumes that
   more than one code could be offered concurrently as well as leaving
   open the possibility of new codes in the future.  Without loss of
   generality in the document we consider that the encoding operations
   compute a linear combination of QUIC packets.  Terms and definitions
   that apply to coding are available in RFC xxxx [nc-taxonomy]

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].








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2.  Design Considerations

2.1.  Framing

   A new QUIC frame type is defined within the current framework
   [quic-basics] to add the error correction feature.  This new frame
   type contains inputs to the negotiated loss recovery algorithm as
   specified by the specific algorithm and coded information.  THis
   frame payload begins with arguments that point to the negotiated
   function that generates the coding coefficients to be applied to the
   remaining payload.  It also indicates the identity of the first
   packet in the coding window and its size as well as other necessary
   input.  There are currently a number of options for identifying the
   coded packets.  Firstly we can assign a new coded sequence number.
   If all packets are encoded in a session, then we can specify which
   packet is the first and with the window size it will be easy to
   recover the packets.  If some packets are encoded and some are not
   then there could be gaps in the numbering that is not due to loss and
   we may need to specify which packets are inside the window using a
   form of run-length-encoding.  We can specify a fixed-length field in
   order to identify the packets.  Secondly, we could use the QUIC
   packet numbering which would reduce the overhead.  This has the same
   functionality as using a sequence number except that in that case the
   gaps in numbering could be due to path migration and not losses Note:
   a reference will be provided in a later version.

2.2.  Coding Symbol

   One of the the design consideration is the definition of the code
   symbol.  In order to minimize the impact on the QUIC design, the QUIC
   loss recovery (QLR) will be applied inside the QUIC encrypted packet
   payloads.  Hence raw packets are used as symbols, the units of
   recovery are what the coding coefficients are applied to.  Any packet
   payloads smaller than the coded payload will be implicitly padded
   with zeros as to prevent the detection of coding on any path.  To
   allow for the coded packets to have more encrypted payload than other
   packets, any QUIC PADDING frames(type 0x00) [quic-basics] will be
   removed from the payload before applying the algorithm.  This new
   frame type contains inputs to the negotiated loss recovery algorithm
   as specified by the specific algorithm and coded information.We want
   to keep the coding implementation simple, provide for code
   negotiation and stay independent of any encryption mechanism.  It is
   thus proposed to apply loss recovery code before the encryption,
   hence to clear data.  This allows the encryption operation to be
   unencumbered by coding.  Hence raw packets will be used as coding
   symbols.  The downside of this approach is that it does not enable
   non-participating middleboxes to add or remove encoding from packets
   but this is considered insignificant compared to the complexities of



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   interacting with security mechanisms.  In addition, it is assumed
   that the the entire packet content will constitute a single source
   symbol.  This choice is motivated by the desire to simplify the
   implementation.  Coding should be applied to all QUIC packets except
   the 0RTT payloads.  0RTT payloads are sent prior to negotiation, and
   the QUIC negotiation mechanism does not allow sending extension
   frames prior to handshake completion.

2.3.  Negotiation

   There are already multiple candidates for the QUIC FEC and we assume
   that others may become available in the future as research
   continues.In order to stay as generic as possible and enable QUIC
   network operators to select their coding technology, it is assumed
   that a coding negotiation will be implemented to select one or more
   codes to be used over a QUIC session.This will be implemented using
   the one step negotiation of the new QUIC negotiation mechanism
   [quic-basics].  Each available coding algorithm should use the
   standard FEC frame [RFC3452] but reserve a different codepoint.  We
   want to ensure that coding negotiation occurs during the QUIC
   handshake and can be used in all short header QUIC packets.  Finally,
   to make the code selection as generic as possible, each algorithm
   should specifies a sequence of coding coefficients or a function to
   generate them, window sizes as necessary as well as meta information
   to ensure the conformant performance of the coding and decoding
   operations

3.  References

3.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

3.2.  Informative References

   [nc-taxonomy]
              Roca et al., V., "draft-irtf-nwcrg-network-coding-
              taxonomy-07", 2018.

   [quic-basics]
              Iyengar, J. and M. Thomson, "draft-ietf-quic-transport-
              09", 2018.

   [RFC3452]  Luby et al., M., "RFC 3452: Forward Error Correction (FEC)
              Building Block", 2002.



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   [RFC5053]  Luby et al., M., "RFC 5053: Raptor Forward Error
              Correction Scheme for Object Delivery", 2007.

   [RFC5510]  Lacan et al., J., "RFC 5510: Reed-Solomon Forward Error
              Correction (FEC) Schemes", 2009.

   [RLNC]     Ho et al., T., "A Random Linear Network Coding Approach to
              Multicast", 2006.

   [Tetrys]   Detchart, J., Lochin, E., Lacan, J., and V. Roca, "draft-
              detchart-nwcrg-tetrys-03", 2016.

Appendix A.  Appendix: Reference Algorithms

   This ID does not mandate nor depends on any coding scheme.  However,
   in order to have an initial implementation with good performance and
   not encumbered by intellectual property and proprietary
   implementations, it is suggested to use the Raptor (RFC 5053) as a
   reference algorithm.  However, since the Raptor code perform badly
   with small blocks, depending on the application, another alternative
   is to use Reed-Solomon (RFC 5510) codes.  It is assumed that other
   candidates that are free of IPR may become candidates in the future.

Appendix B.  Appendix: Participating Middleboxes

   The coding approach described in this document does allow on path
   elements that have the ephemeral keys to decrypt packets and add or
   remove FEC packets.

Appendix C.  Appendix: APIS

   It is planned that the QUIC coding mechanism will conform to any
   common API defined in the research group.

Authors' Addresses

   Ian Swett
   Google
   Cambridge, MA
   US

   Email: ianswett@google.com









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   Marie-Jose Montpetit
   Triangle Video
   Boston, MA
   US

   Email: marie@mjmontpetit.com


   Vincent Roca
   INRIA
   Grenoble, France
   US

   Email: vincent.roca@inria.fr





































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