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QUIC                                                               Q. An
Internet-Draft                                                    D. Liu
Intended status: Standards Track                                  Y. Liu
Expires: September 6, 2020                                  Alibaba Inc.
                                                           March 5, 2020


         Key Components for Multipath QUIC Traffic Distribution
            draft-an-multipath-quic-traffic-distribution-00

Abstract

   This document describes several key components for Multipath QUIC
   traffic distribution.  The key components remain compliant with the
   current Multipath Extensions for QUIC (MP-QUIC) design.

Status of This Memo

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

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   This Internet-Draft will expire on September 6, 2020.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   2
   3.  Packet Scheduling . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Stream Management . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Congestion Control  . . . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The QUIC connection migration feature, described in more details in
   [I-D.ietf-quic-transport], enables QUIC to sustain a connection over
   multiple paths, but still there is a void to specify simultaneous
   usage of available paths for a single connection.
   [I-D.deconinck-quic-multipath] describes how to use multiple paths
   simultaneously for a single QUIC connection, but how to spread
   packets over multiple paths following a traffic distribution policy,
   and how to receive packets from multiple paths, are not specified.
   If not standardized, implementers would still not know how to
   transmit data over multipath QUIC.

   There are several use scenarios about traffic distribution over
   multipath QUIC.  One would be stream media transmission.  A typical
   example is Internet live video broadcasting.  It has high requirement
   on data transmission speed but packet loss rate is lowly prioritized.
   In this case, multipath QUIC can provide a better utilization of
   multiple path bandwidth.  Another use scenario is highly reliable
   real-time data transmission, which is sensitive to packet loss.  In
   this case, redundancy data can be transmitted over multipath QUIC.
   To support the requirements of these use scenarios, multipath QUIC
   traffic distribution needs to be standardized.

   In this document, it focuses on the description of several key
   components which are necessary to support the implementation of
   Multipath QUIC traffic distribution.  The key components include
   packet scheduling, congestion control and stream management.

2.  Notational Conventions

   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].






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3.  Packet Scheduling

   Given the established multiple QUIC paths, packet scheduling
   determines which path(s) to deliver packets, how many packets are
   delivered on a specific QUIC path, which packets are delivered on a
   specific QUIC path.

   Figure 1 illustrates the process of packet scheduling.


                     Path Performance
                       Measurement
   Original                 |             +-+-+-+
   Data                     V         +-> | | | |   Path 1
                     +-+-+-+-+-+-+-+  |   +-+-+-+
   +-+-+-+-+         |    Packet   |  |   +-+
   |    ...|  ->     | Distribution| -+-> | |
   +-+-+-+-+         +-+-+-+-+-+-+-+  |   +-+
                                      |   +-+-+
                                      +-> | | |     Path i
                                          +-+-+


         Figure 1: Processing Flow of Data Sending Over Multipath

   Since the conditions of each path are different, the different paths
   need to be measured and selected, in order to pick out paths with
   better performance, and distribute packets to different paths
   according to path performance.

   There are many traffic distribution mechanisms.  Some are based on
   lowest RTT, while some are based on transmission speed and packet
   loss rate, which need further evaluation for MPQUIC.

   In addition, in scenario where there is large performance difference
   between multiple QUIC paths, how to select path(s) and how to
   distribute packets need to be considered.  Possible solution could be
   discarding the path(s) with low performance (packet loss rate is
   higher than threshold, like 5%), or only transmitting redundancy
   packets on path(s) with low performance.

4.  Stream Management

   It is recommended to support the configuration of transmission
   policies for different QUIC streams.  This can be supported by multi
   priority queue.  Figure 2 illustrates the concept of stream
   management.




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          stream                      Multi priority queue
                                       +-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+      +----------> |               |
   |               |----- |            +-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+      |
                          |            +-+-+-+-+-+-+-+-+
         ...              +----------> |               |
                          +----------> +-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+      |                   ...
   |               |----- |            +-+-+-+-+-+-+-+-+
   +-+-+-+-+-+-+-+-+      +----------> |               |
                                       +-+-+-+-+-+-+-+-+


                Figure 2: Multipath QUIC Stream Management

   For example, high priority streams can be delivered first, and even
   reinjection, while reinjection will not apply for low priority
   streams.

5.  Congestion Control

   Congestion control is indispensable for MPQUIC.  There can be two
   options: decoupled congestion control, or coupled congestion control.

   For decoupled congestion control, the congestion control policy of
   each path is decoupled, which is beneficial for maximizing the
   bandwidth utilization of each path.

6.  IANA Considerations

   This document makes no request of IANA.

7.  Normative References

   [I-D.deconinck-quic-multipath]
              De Coninck, Q. and O. Bonaventure, "Multipath Extensions
              for QUIC (MP-QUIC)", draft-deconinck-quic-multipath-03
              (work in progress), August 2019.

   [I-D.ietf-quic-transport]
              Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
              and Secure Transport", draft-ietf-quic-transport-23 (work
              in progress), September 2019.







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   [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>.

Authors' Addresses

   Qing An
   Alibaba Inc.

   Email: anqing.aq@alibaba-inc.com


   Dapeng Liu
   Alibaba Inc.

   Email: max.ldp@alibaba-inc.com


   Yanmei Liu
   Alibaba Inc.

   Email: miaoji.lym@alibaba-inc.com




























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