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QUIC                                                               Q. An
Internet-Draft                                              Alibaba Inc.
Intended status: Standards Track                                   Z. Li
Expires: January 7, 2021                                         ICT-CAS
                                                                  Y. Liu
                                                            Alibaba Inc.
                                                            July 6, 2020


        Enabling application policy-awareness in Multipath QUIC
             draft-an-multipath-quic-application-policy-00

Abstract

   This document describes an application policy-awareness method for
   Multipath QUIC, to enable taking applications' demands into account
   when managing paths or scheduling packets in Multipath QUIC.

Status of This Memo

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   This Internet-Draft will expire on January 7, 2021.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  What is Application Policy-awareness in Multipath QUIC  . . .   3
   4.  Per-connection Policy . . . . . . . . . . . . . . . . . . . .   4
   5.  Per-stream Intent . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The availability of multiple network interfaces in devices enables
   the use of multiple paths between two end points for robust and
   (possibly) fast data delivery.  Multi-path TCP (MPTCP) was designed
   to leverage off such an availability.  It has been adopted by
   operating systems and ISPs.  A major design principle of MPTCP is
   that it must be usable by applications through existing SOCKET APIs.
   That said, it shields the underlying multiple paths for the
   applications, which may be not even aware the use of multiple path
   transmission.  While this implements the backward compatibility with
   TCP, it also leaves the applications out of the control loop of the
   transport.  Nevertheless, applications may have completely different
   QoE requirements---the interactive applications are delay sensitive,
   while the video streaming are more throughput sensitive.  There is
   thus a trend of cross-layer design that tries to take applications'
   demands into account when managing paths or scheduling packets in
   MPTCP [MP-DASH][WN][AD-MPTCP][SMAPP].

   We thus advocate the idea of application policy awareness in multi-
   path transport, which is to separate the 'control plane' from the
   `data plane' like in software defined networking.  The 'control
   plane' takes applications' high-level demands (a.k.a intent) as input
   to generate the corresponding policies, which later are deployed on
   the 'data plane'.  The 'data plane' maps users policies to the
   'actions', which control the path management, packet scheduling and
   other functionalities that the transport implements.  For instance,
   the 'actions' for path management may include "backup", "full mesh"
   and "ndiffports", while the 'actions' for packet scheduling may
   designate whether ECF [ECF] or DEMS [BSC] is used for path selection,
   and may also impose a traffic split ratio among paths.  Each
   connection then can have a customized multipath transport.





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   Since MPTCP is implemented in OS kernel, it is not easy for
   application providers to incorporate the above idea into MPTCP to
   improve the applications' performance.  QUIC, on the other hand,
   implements a UDP-based transport, which enables the transport to be
   bundled into applications and quickly deployed in end users' devices.
   MPQUIC extends QUIC to multipath scenarios.  Nevertheless, the basic
   MPQUIC [MPQUIC-Design] acts much like MPTCP, except it uses QUIC (as
   opposed to TCP).  That said, the current MPQUIC implementation does
   not support application policy-aware transport.

   A straight solution for MPQUIC to enable the interaction between
   applications and transport is to let applications to access/change
   every single logic of the packet scheduling and path management, or
   export callback functions as in [SMAPP].  This however will result in
   a complex mix between applications and transport because of limited
   abstraction.  And perhaps more importantly, it requires application
   developers to understand the details of the underlying transport.

   This document describes an application policy-awareness method for
   Multipath QUIC, to enable taking applications' demands into account
   when managing paths or scheduling packets in Multipath QUIC.  The
   method remains compliant with the current Multipath Extensions for
   QUIC [I-D.deconinck-quic-multipath] design.

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].

3.  What is Application Policy-awareness in Multipath QUIC

   We advocate a more practical alternative (See Figure 1), where 1).
   the `control plane' provides primitives to applications to express
   their policies (intent); 2). the `data plane' abstracts execution
   models for application policies and generates the corresponding
   composed `actions'.














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               per-stream intent                   per-conn policy
    Control e.g. stream prioirity      e.g. path preference, path mode,
    Plane                                        deadline-aware etc
               |                                        |
    -----------|----------------------------------------|-------------
               V                                        V
    Data  +--------+ -                      +------------------------+
    Plane |        |  |                     |                        |
          +--------+  |                     |                +-----+ |
                      |                     |             +->| ... | |
          +--------+  |                     |             |  +-----+ |
          |        |  |                     |             |  +-----+ |
          +--------+  |                     |             +->| ... | |
                      |                     |             |  +-----+ |
          +--------+  | +----------+ chunks |+----------+ |          |
          |        |  ->|  stream  |------->||  packet  |-+    ...   |
          +--------+  | |scheduling|        ||scheduling| |          |
             ...      | +----------+        |+----------+ |  +-----+ |
          +--------+  |                     |             +->| ... | |
          |        |  |                     |             |  +-----+ |
          +--------+  |                     |             |  +-----+ |
                      |                     |             +->| ... | |
          +--------+  |                     |                +-----+ |
          |        |  |                     |           path manager |
          +--------+ -                      +------------------------+
            streams



    Figure 1: Application Policy Awareness in Multi-path QUIC framework

4.  Per-connection Policy

   An application imposes per-connection policy through the primitives
   provided by the control plane.  Some examples of policies are path
   preference (e.g. a Wi-Fi path is preferred twice than a cellular
   path), path model (e.g. full mesh, ndiffports, backup).  The packet
   scheduling component and the path manager at the data plane will act
   based on these indications for path selection and data transmission.
   We assume the policies are 'soft'---the policies are not a must.
   Instead, the data plane will follow the policies as much as possible.

   Let us take real-time interaction applications as an example to
   illustrate the basic idea.  The applications are indeed delay
   sensitive but data volume is often low. 3 types of policies may be
   used by different applications, as shown in Table 1 where we assume
   only two paths are available (Wi-Fi and Cellular)




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   +-----+-----------------+-------------+------------+----------------+
   | No. |   Application   | Application | Underlying |   Underlying   |
   |     | defined policy: |   defined   |  action:   |  action: Path  |
   |     |    Path mode    |   policy:   |   Packet   |     mngm.      |
   |     |                 |     Path    | Scheduling |                |
   |     |                 |  Preference |            |                |
   +-----+-----------------+-------------+------------+----------------+
   |  1  |   Wi-Fi=full,   |   Wi-Fi=1,  |    full    |       /        |
   |     |  Cellular=full  |  Cellular=1 | redundant  |                |
   |     |                 |             |            |                |
   |  2  |   Wi-Fi=full,   |   Wi-Fi=1,  |    full    |    activate    |
   |     | Cellular=backup |  Cellular=1 | redundant  |     backup     |
   |     |                 |             |            |   interfaces   |
   |     |                 |             |            |    when the    |
   |     |                 |             |            |  active one's  |
   |     |                 |             |            | performance is |
   |     |                 |             |            |  lower than X  |
   |     |                 |             |            |     for 5s     |
   |     |                 |             |            |                |
   |  3  |   Wi-Fi=full,   |   Wi-Fi=2,  | partially  |       /        |
   |     |  Cellular=full  |  Cellular=1 | redundant  |                |
   +-----+-----------------+-------------+------------+----------------+

     Table 1: Example policies of a real-time interaction application

   The first type of policies would like to use two paths equally, and
   because the applications are delay sensitive, the actions will be
   'full redundant' for the packet scheduling---two paths send the same
   data.  The second type of policies, on the other hand, would like to
   use the Wi-Fi interface (possibly because of data charge) if
   possible.  But if two paths have to be activated at the same time due
   to the lower performance of Wi-Fi, then the two paths are with same
   the preference.  So, the corresponding actions will be will be 'full
   redundant' for the packet scheduling, and the path management
   component will monitor the performance of the active interface and
   activate the backup one if the performance is lower than a threshold
   for a short period of time (e.g. 5 seconds).  The third type of
   policies would like to use the two interfaces at the same time, but
   Wi-Fi is preferred twice as the cellular one.  The actions will take
   this into consideration, and implement partial redundant transmission
   over the cellular Interface.

   Likewise, we can define a mapping between the policies of different
   types of applications and the actions in the data plane.  We leave
   the design of such a mapping to the designers.

   TODO: Add design of such a mapping.




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5.  Per-stream Intent

   Per-stream intent is a unique feature provided by (MP)QUIC---it is
   implemented through the multiple streams in QUIC.  Streams can be
   associated with priorities to implement applications intent.  For
   instance, objects in a web page may be dependent on others and thus
   have different priorities [MPQUIC-Scheduler].  A priority-aware
   packet scheduling algorithm will improve the performance notably.



    High priority  /\  +---------+
                   ||  |         |
                   ||  +---------+
                   ||  +---------+
                   ||  |         |
                   ||  +---------+
                   ||     ...          User-defined priority
                   ||  +---------+
    Low priority   ||  |         |
                   ||  +---------+
    -----------------------------------------------------------
    High priority  /\  +---------+
                   ||  |         |
                   ||  +---------+
                   ||  +---------+
                   ||  |         |
                   ||  +---------+
                   ||     ...          Default priority
                   ||  +---------+
    Low priority   ||  |         |
                   ||  +---------+



                         Figure 2: Stream priority

   We envision a priority management scheme of two separated priority
   ranges (see Figure 2).  The user-defined priority ranges are those
   streams that the applications explicitly designate the priorities,
   where the default priority ranges include the streams with no
   priority values set by the applications.  Only when the streams in
   the user-defined ranges have no data sent, the data in the streams in
   the default priority ranges can be sent.  In the same range, one can
   use the weighted round robin for scheduling---the higher-priority
   streams get more quantum for data sending in each round.  One can
   also dynamically set/change the priorities of the streams in the
   default priority ranges to enable short stream first if needed.



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   We list in Table 2 some applications that can be benefited from the
   above priority-aware stream management scheme.

  +---------------------+-----------------------------+----------------+
  |     Application     |       Priority setting      |    Benefits    |
  +---------------------+-----------------------------+----------------+
  |         Web         |   Setting stream priority   |  Reduced page  |
  |                     |    based on the objects'    |   load time    |
  |                     |          priorities         |                |
  |                     |      [MPQUIC-Scheduler]     |                |
  |                     |                             |                |
  |     Photo album     |  Default setting; dynamical |  Reduced load  |
  |                     |  changing priority to mimic |  time of the   |
  |                     |  shorted stream first like  |  first image;  |
  |                     |  in flow scheduling in data |   images of    |
  |                     |        centers [CDC]        |   small size   |
  |                     |                             |    will be     |
  |                     |                             |   displayed    |
  |                     |                             |     first      |
  |                     |                             |                |
  |    Live streaming   | The chunks or GoPs with the |  Low startup   |
  |   (viewing) / VoD   |   closest deadline are put  |   delay, low   |
  |                     | into the stream with higher |   buffering    |
  |                     |       priorities. This      |     ratio      |
  |                     |    essentially implements   |                |
  |                     |     deadline-aware data     |                |
  |                     |         transmission        |                |
  |                     |                             |                |
  |   Live streaming:   |  The original segments are  |    Enhanced    |
  | broadcaster->server | put into the streams in the | shift-viewing  |
  |                     |    user-defined priority    |   quality of   |
  |                     |  range, while the enhanced  |    services    |
  |                     |  segments are put into the  |   [Vantage]    |
  |                     |    streams in the default   |                |
  |                     |        priority range       |                |
  +---------------------+-----------------------------+----------------+

    Table 2: Example applications benefited from priority-aware stream
                             management scheme

   TODO: Add priority management solution.

6.  IANA Considerations

   This document makes no request of IANA.






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7.  Informative References

   [AD-MPTCP]
              Froemmgen, A., Rizk, A., Erbshaeusser, T., Weller, M.,
              Koldehofe, B., Buchmann, A., and R. Steinmetz, "A
              programming model for application-defined multipath TCP
              scheduling", Proceedings of the 18th ACM/IFIP/USENIX
              Middleware Conference (Middleware '17). Association for
              Computing Machinery, New York, NY, USA, 134-146., 2017,
              <https://doi.org/10.1145/3135974.3135979>.

   [BSC]      Guo, Y., Nikravesh, A., Mao, Z., Qian, F., and S. Sen,
              "Accelerating Multipath Transport Through Balanced Subflow
              Completion", Proceedings of the 23rd Annual International
              Conference on Mobile Computing and Networking (MobiCom
              '17). Association for Computing Machinery, New York, NY,
              USA, 141-153., 2017,
              <https://doi.org/10.1145/3117811.3117829>.

   [CDC]      Bai, W., Chen, L., Chen, K., Han, D., Tian, C., and H.
              Wang, "Information-agnostic flow scheduling for commodity
              data centers", Proceedings of the 12th USENIX Conference
              on Networked Systems Design and Implementation (NSDI'15).
              USENIX Association, USA, 455-468., 2015.

   [ECF]      Lim, Y., Nahum, E., Towsley, D., and R. Gibbens, "ECF: An
              MPTCP Path Scheduler to Manage Heterogeneous Paths",
              Proceedings of the 13th International Conference on
              emerging Networking EXperiments and Technologies (CoNEXT
              '17). Association for Computing Machinery, New York, NY,
              USA, 147-159., 2017,
              <https://doi.org/10.1145/3143361.3143376>.

   [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.

   [MP-DASH]  Han, B., Qian, F., Ji, L., and V. Gopalakrishnan, "MP-
              DASH: Adaptive Video Streaming Over Preference-Aware
              Multipath", Proceedings of the 12th International on
              Conference on emerging Networking EXperiments and
              Technologies (CoNEXT '16). Association for Computing
              Machinery, New York, NY, USA, 129-143., 2016,
              <https://doi.org/10.1145/2999572.2999606>.






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   [MPQUIC-Design]
              De Coninck, Q. and O. Bonaventure, "Multipath QUIC: Design
              and Evaluation", Proceedings of the 13th International
              Conference on emerging Networking EXperiments and
              Technologies (CoNEXT '17). Association for Computing
              Machinery, New York, NY, USA, 160-166., 2017,
              <https://doi.org/10.1145/3143361.3143370>.

   [MPQUIC-Scheduler]
              Wang, J., Gao, Y., and C. Xu, "A Multipath QUIC Scheduler
              for Mobile HTTP/2", Proceedings of the 3rd Asia-Pacific
              Workshop on Networking 2019 (APNet '19). Association for
              Computing Machinery, New York, NY, USA, 43-49., 2019,
              <https://doi.org/10.1145/3343180.3343185>.

   [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>.

   [SMAPP]    Hesmans, B., Detal, G., Barre, S., Bauduin, R., and O.
              Bonaventure, "SMAPP: towards smart multipath TCP-enabled
              applications", Proceedings of the 11th ACM Conference on
              Emerging Networking Experiments and Technologies (CoNEXT
              '15). Association for Computing Machinery, New York, NY,
              USA, Article 28, 1-7., 2015,
              <https://doi.org/10.1145/2716281.2836113>.

   [Vantage]  Ray, D., Kosaian, J., Rashmi, K., and S. Seshan, "Vantage:
              optimizing video upload for time-shifted viewing of social
              live streams", Proceedings of the ACM Special Interest
              Group on Data Communication (SIGCOMM '19). Association for
              Computing Machinery, New York, NY, USA, 380-393., 2019,
              <https://doi.org/10.1145/3341302.3342064>.

   [WN]       Cui, Y., "Wireless Network Instabilities in the Wild:
              Measurement, Applications (Non)Resilience, and OS Remedy",
              2019 IEEE/ACM Transactions on Networking, vol. 27, no. 1,
              pp. 214-230., 2019, <10.1109/TNET.2018.2885872>.

Authors' Addresses

   Qing An
   Alibaba Inc.

   Email: anqing.aq@alibaba-inc.com





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   Zhenyu Li
   ICT-CAS

   Email: zyli@ict.ac.cn


   Yanmei Liu
   Alibaba Inc.

   Email: miaoji.lym@alibaba-inc.com









































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