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Optimizing ACK mechanism for QUIC
draft-li-quic-optimizing-ack-in-wlan-05

Document Type Active Internet-Draft (individual)
Authors Tong Li , Kai Zheng , Rahul Jadhav , Jiao Kang
Last updated 2022-11-07
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Additional resources ROADMAP OF STANDARDIZING TACK
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draft-li-quic-optimizing-ack-in-wlan-05
QUIC                                                               T. Li
Internet-Draft                                Renmin University of China
Intended status: Experimental                                   K. Zheng
Expires: 12 May 2023                                         R.A. Jadhav
                                                                 J. Kang
                                                                  Huawei
                                                         8 November 2022

                   Optimizing ACK mechanism for QUIC
                draft-li-quic-optimizing-ack-in-wlan-05

Abstract

   The dependence on frequent acknowledgments (ACKs) is an artifact of
   current transport protocol designs rather than a fundamental
   requirement.  This document analyzes the problems caused by
   contentions and collisions on wireless medium between data packets
   and ACKs in WLAN and it proposes an ACK mechanism that minimizes the
   intensity of ACK Frame in QUIC, improving the performance of
   transport layer connection.

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 12 May 2023.

Copyright Notice

   Copyright (c) 2022 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 carefully, as they describe your rights

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

Table of Contents

   1.  Requirements Language . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Overview of Standards on ACK Mechanism  . . . . . . . . . . .   3
   4.  Optimized ACK Mechanism for QUIC  . . . . . . . . . . . . . .   4
     4.1.  Reducing ACK intensity  . . . . . . . . . . . . . . . . .   4
     4.2.  OWD-based RTTmin estimation . . . . . . . . . . . . . . .   6
     4.3.  Sender-Side Operation . . . . . . . . . . . . . . . . . .   7
     4.4.  Receiver-side Operation . . . . . . . . . . . . . . . . .   8
     4.5.  Generating ACK  . . . . . . . . . . . . . . . . . . . . .   8
     4.6.  Modification to QUIC Protocol . . . . . . . . . . . . . .   8
       4.6.1.  Transport Parameter: ack-intensity-support  . . . . .   8
       4.6.2.  ACK-INTENSITY Frame . . . . . . . . . . . . . . . . .   9
       4.6.3.  TIMESTAMP Frame . . . . . . . . . . . . . . . . . . .   9
       4.6.4.  ACK Delay Redefinition  . . . . . . . . . . . . . . .  10
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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 [RFC2119].

2.  Problem Statement

   High-throughput transport over wireless local area network (WLAN)
   becomes a demanding requirement with the emergence of 4K wireless
   projection, VR/AR-based interactive gaming, Metaverse, and more.
   However, the shared nature of the wireless medium induces contention
   between data transport and backward signaling, such as
   acknowledgment.  ACKs share the same medium route with data packets,
   causing similar medium access overhead despite the much smaller size
   of the ACKs.  Contentions and collisions, as well as the wasted
   wireless resources by ACKs, lead to significant throughput decline on
   the data path.  This draft follows the roadmap as depicted in [AOD]

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3.  Overview of Standards on ACK Mechanism

   [RFC9000] specifies a simple delayed ACK mechanism that a receiver
   can send an ACK for every other packet, and for every packet when
   reordering is observed, or when the max_ack_delay timer expires.
   However, this ACK mechanism may not match the number of ACKs to the
   transport's required intensity under different network conditions.
   For example, when the data throughput of a WLAN transport is
   extremely high, QUIC will generate a large number of ACKs.  In this
   case, minimizing the ACK intensity of QUIC is not only a win for data
   throughput improvement but also a win for energy and CPU efficiency.

   [RFC1122] and [RFC5681] were two core functionality standards that
   introduced delayed ACK, which was the default acknowledgment
   mechanism in most Linux distributions.  [RFC4341] and [RFC5690]
   described an acknowledgment congestion control mechanism in which the
   minimum ACK frequency allowed is twice per send window.  [RFC3449]
   discussed the imperfection and variability of TCP's acknowledgment
   mechanism because of asymmetric effects and recommended scaling ACK
   frequency as a mitigation to these effects.  These RFCs reveal that
   the dependence on frequent ACKs is an artifact of current transport
   protocol designs rather than a fundamental requirement.  Based on
   this insight, some work-in-progress IETF drafts have paid great
   attention to ACK scaling technologies in both TCP and QUIC working
   groups.

   First of all, [ACK-PULL] proposed the TCP ACK pull mechanism, which
   allows a sender to request the ACK for a data segment to be sent
   without additional delay by the receiver.  This helps in some cases
   when the delayed ACKs degrade transport performance.

   Instead of pulling more ACKs, [QUIC-SCALING] recommended that
   reducing the ACK frequency by sending an ACK for at least every 10
   received packets and [QUIC-SATCOM] recommended an ACK frequency of
   four ACKs every round-trip time (RTT), aiming to reduce link
   transmission costs for asymmetric paths.

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   Different from using an empirical value of ACK frequency, instead, we
   try to improve the scalability by proposing a novel ACK mechanism
   named Tame ACK (TACK), whose frequency is a function of bandwidth-
   delay product of network connections.  The detailed TCP-based
   implementation (i.e., TCP-TACK) details and evaluation results have
   been shown in our prior work [Tong].  TCP-based implementation
   depends on the middleboxes to permit the extended-option-packets
   through, which might limit applicable scenarios.  While QUIC is a
   flexible framework of transport protocol that uses UDP as a substrate
   to avoid requiring changes to legacy operating systems and
   middleboxes, and encrypts most of the packets including ACKs to avoid
   incurring a dependency on middleboxes.  Hence, this draft focuses on
   applying TACK to optimize the ACK mechanism for QUIC.

   It is worth noting that [IYENGAR-ACK] has proposed an extension of
   sender controlled ACK-FREQUENCY frame for QUIC, which is possible to
   be reused to help the sender sync the dynamically adjusted TACK
   frequency with the receiver in this case.

4.  Optimized ACK Mechanism for QUIC

4.1.  Reducing ACK intensity

   ACK intensity can be quantified by the unit of Hz, i.e., number of
   ACKs per second.  Byte-counting ACK and periodic ACK are two
   fundamental ways to reduce ACK intensity on the transport layer.

   1.  Byte-counting ACK: ACK intensity is controlled by sending an ACK
   for every L (L >= 2) incoming full-sized packets, in which the packet
   size equals to the Max Packet Size (set in the max_packet_size
   parameter in QUIC).  The intensity of byte-counting ACK (f_b) is
   proportional to data throughput (bw):

   f_b = bw/L*max_packet_size (1)

   In general, f_b can be reduced by setting a large value of L.
   However, for a given L, f_b increases with bw.  This means when data
   throughput is extremely high, the ACK intensity still might be
   comparatively large.  In other words, the intensity of byte-counting
   ACK changes proportionately with bandwidth.

   2.  Periodic ACK: Byte-counting ACK's unbounded intensity can be
   attributed to the coupling between ACK sending and packet arrivals.
   Periodic ACK can decouple ACK intensity from packet arrivals,
   achieving a bounded ACK intensity when bw is high.  The intensity of
   periodic ACK (f_pack) is:

   f_pack = 1/alpha (2)

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   Where alpha is the time interval between two ACKs and is a function
   of RTT.  However, when bw is extremely low, the ACK intensity is
   always as high as that in the case of a high throughput.  In other
   words, the intensity of periodic ACK is unadaptable to bandwidth
   change, which wastes resources.

   Following the design of TACK [Tong], we combine the above two ways,
   and set the minimum ACK intensity in a QUIC connection as f_quic =
   min{f_b,f_pack}. Through Equations (1) and (2), we have

   f_quic = min{bw/(L*max_packet_size), 1/alpha} (3)

   We set alpha = RTTmin/beta, which means sending beta ACKs per RTTmin.
   RTTmin is the minimum RTT observed for a given network path.  As a
   consequence, the minimum ACK intensity in a QUIC connection can be
   given as follow:

   f_quic = min{bw/(L*max_packet_size), beta/RTTmin} (4)

   where beta indicates the number of ACKs per RTT, and L indicates the
   number of full-sized data packets counted before sending an ACK.  To
   minimize the ACK intensity, a smaller beta or a larger L is expected.
   Sara Landstrom et al. has given a lower bound of beta in [Sara],
   i.e., beta >= 2.  We have further given an upper bound of L, which
   can be derived according to the loss rate on the data path (plr_data)
   and the ack path (plr_ack), i.e., L <=
   feedback_info/(plr_data*plr_ack).  Where feedback_info denotes the
   amount of information carried by an ACK.  The detailed derivation can
   be refered in [Tong].

   Qualitatively, periodic ACK is applied when bandwidth-delay product
   (bdp) is large (i.e., bdp >= beta*L* max_packet_size), and byte-
   counting ACK is applied when bdp is small (i.e., bdp < beta*L*
   max_packet_size).

   In terms of a transport with a large bdp, beta = 2 should be
   sufficient to ensure utilization, but the large bottleneck buffer
   (i.e., one bdp) makes it necessary to acknowledge data more often.
   In general, the minimum send window (SWNDmin) can be roughly
   estimated as follow:

   SWNDmin = beta*bdp/(beta-1) (5)

   Ideally, the bottleneck buffer requirement is decided by the minimum
   send window, i.e., SWNDmin - bdp.  Since doubling the ACK frequency
   reduces the bottleneck buffer requirement substantially from 1 bdp to
   0.33 bdp, beta = 4 is RECOMMENDED to provide redundancy [Sara], being
   more robust in practice.

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4.2.  OWD-based RTTmin estimation

   In this document, the RTTmin is the minimum RTT samples observed at
   the sender for a given network path during a period of time, and
   OWDmin is the minimum OWD samples observed on the same network path
   during a period of time.

   An RTT estimation system contains a sender and a receiver.  The
   sender can hardly generate per-packet RTT samples, which is the root
   cause of the minimum RTT estimation biases in the case of sending
   fewer ACKs.  When multiple packets carrying departure timestamps are
   transported between endpoints via the same path , an RTT of this path
   can be sampled at the sender upon receiving an ACK frame.  However,
   when sending fewer ACK frames, more data packets might be received
   during the ACK interval, generating only one RTT sample among
   multiple packets is likely to result in biases.  For example, a
   larger minimum RTT estimate.  In general, the higher the throughput,
   the larger the biases.  One alternative way to reduce biases can be
   that, each ACK frame carries multiple timestamps (as well as ACK
   delays in [RFC9002]) for the sender to generate more RTT samples.
   However, (1) the overhead is high, which is unacceptable especially
   for high-bandwidth transport.  Also, (2) the number of data packets
   might be far more than the maximum number of timestamps that an ACK
   frame is capable of carrying.  Since the receiver is capable to
   monitor per-packet state, the one-way delay (OWD) of each packet can
   be easily computed according to the departure timestamps (carried in
   the packet) and the arrival timestamps of each packet.  In this case,
   QUIC SHOULD adopt the OWD-based RTTmin estimation.  The rationale is
   that the variation of OWD reflects the variation of RTT over near-
   symmetric links.  The OWD-based RTTmin estimation requires the sender
   to record the departure timestamp in each ack-eliciting packet.
   Meanwhile, at the receiver, the per-packet OWD samples SHOULD be
   computed upon packet arrivals and a function of computing the minimum
   OWD SHOULD be newly added.  The receiver then generates an ACK frame
   to the sender, in which the ACK delay and departure timestamp for the
   packet that achieves the minimum OWD is reported.  The ACK delay is
   defined as the delay incurred between when the packet is received and
   when the ACK frame is sent.  Based on the information reported by the
   incoming ACK frames and the ACK arrival timestamps, the sender can
   generate RTT samples and then compute RTTmin accordingly.

   In this document, RTTmin is used to update the ACK intensity.  In
   general, RTTmin can also be used by other modules.  For example, some
   congestion controllers depends on RTTmin to estimate the congestion
   window [Neal].  RTTmin is also used by QUIC loss detection to reject
   implausibly small rtt samples [RFC9002].

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4.3.  Sender-Side Operation

   According to Formula (4), the run-time ACK intensity in QUIC are
   decided by bw, and RTTmin.  Generally, the RTTmin and bw are
   calculated at the sender.

   Before estimating the RTTmin, the RTT samples should be computed
   based on the ACK frames collected during a period of time.  Assume
   that a packet is sent by the sender at time t_1 and arrives at time
   t_3, and the ACK frame is sent at time t_4.  The ACK delay can be
   computed at the receiver.  For example, the receiver computes the ACK
   delay delta_t = t_4 - t_3, and syncs the ACK delay to the sender via
   an ACK frame.  The ACK delay can also be computed at the sender.  For
   example, the receiver directly syncs an ACK frame carrying t_4 and
   t_3 to the sender, the sender then computes the ACK delay delta_t =
   t_4 - t_3.

   The sender therefore computes an RTT sample according to delta_t,
   t_1, and the arrival time (t_2) of the ACK frame, i.e., RTT_sample =
   t_2 - t_1 - delta_t.  Measuring delta_t at the receiver assures an
   explicit correction for a more accurate RTT estimate.  RTT samples
   SHOULD be smoothed using exponentially weighted moving average (EWMA)
   as specified in [RFC6298].  The sender then computes the RTTmin
   according to these RTT samples during a period of time.

   The bw estimation can be acquired in a similar manner to BBR [Neal].
   Since minimizing the ACK intensity induces excessive ACK delay, the
   value of bw may be the average value over a long period of time.
   However, the biases introduced in ACK intensity computation is
   limited.

   After computing the f_quic, the sender periodically syncs it to the
   receiver to update the intensity of ACK Frame by sending a new ACK-
   INTENSITY frame.

   The sender SHOULD generate an ACK-INTENSITY frame on a regular basis.
   For example, when the change of f_quic exceeds a threshold, the ACK-
   INTENSITY frame should be sent to update the ACK intensity in time.
   The interval of ACK-INTENSITY frame can also be set according to the
   update window of RTTmin and bw.

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4.4.  Receiver-side Operation

   Currently, the QUIC receiver reports ACK delays for only the largest
   acknowledged packet in an ACK frame, hence an RTT sample is generated
   using only the largest acknowledged packet in the received ACK frame.
   For a more accurate RTTmin estimate when sending fewer ACK frames,
   QUIC SHOULD adopt the OWD-based RTTmin estimation.  The OWD-based
   RTTmin estimation requires the QUIC receiver to filter the departure
   timestamp for the packet that achieves the minimum OWD during the
   interval between two ACK frames and report the ACK delay of this
   packet.  Whether redefining the meaning of ACK delay or not, it
   depends on the negotiation between endpoints of the QUIC connection.

   Upon packet arrivals, the receiver is capable to generate per-packet
   OWD samples according to the difference between packet departure
   timestamp and packet arrival timestamp.  The receiver then computes
   the minimum OWD by comparing the per-packet OWD samples.  The OWD
   estimation does not require clock synchronization here because the
   relative values are adopted.

   Afterwards, based on the ACK delay and the departure timestamp
   corresponding to the packet that achieves the minimum OWD, the sender
   calculates the RTT of this packet as a minimum RTT sample.
   Ultimately, the minimum RTT is computed according to these minimum
   RTT samples.

   The ACK Delay field SHOULD be carried in the ACK Frame.  Other fields
   carried in the ACK frame have the same meaning as defined in
   [RFC9002].

   The receiver adopts the newly updated ACK intensity once it receives
   the ACK-INTENSITY frame from the sender.

4.5.  Generating ACK

   The newly proposed ACK mechanism SHOULD be applied when there is no
   out-of-order delivery.  When reordering happens, the ACK Frame SHOULD
   be generated immediately.

4.6.  Modification to QUIC Protocol

4.6.1.  Transport Parameter: ack-intensity-support

   A new field named ack-intensity-support should be added for
   negotiation between both parties whether starting the dynamic ACK
   intensity function in QUIC connection.  The endpoints sends this
   parameter during handshakes.  Only when both parties agree, ACK
   intensity refreshment can be adopted.

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   ack-intensity-support (0x XX):This parameter has two values (0 or 1)
   specifying whether the sending endpoint is willing to adopt ACK
   intensity refreshment.  When the value is set as 1, it means that the
   sending endpoint want to start ACK intensity refreshment during
   connection.  When the value is set as 0, it means that the sending
   endpoint does not support this function.

4.6.2.  ACK-INTENSITY Frame

   An ACK-INTENSITY frame is shown in Figure 1.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             0x b0(i)                            ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number(i)                    ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       ACK Intensity (i)                     ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 1: ACK-INTENSITY Frame

   An ACK-INTENSITY frame contains the following fields:

   Sequence Number: A variable-length integer indicating the sequence
   number assigned to the ACK-INTENSITY frame by the sender.

   ACK Intensity: A variable-length integer indicating the updated
   f_quic calculated by the sender.

   ACK-INTENSITY frames are ack-eliciting.  However, their loss does not
   require retransmission.

   Multiple ACK-INTENSITY frames SHOULD be generated by the sender
   during a connection to notify the receiver the variation of ACK
   intensity requirement under network dynamics.

4.6.3.  TIMESTAMP Frame

   Instead of the invasive way of adding a new field in the QUIC public
   packet header, it is RECOMMENDED that a new frame be added for
   exchanging the departure timestamp of each packet.

   A TIMESTAMP frame is shown in Figure 2.

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             0x b1(i)                            ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Departure Timestamp (i)                   ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 2: TIMESTAMP Frame

   A TIMESTAMP frame contains the following fields:

   Departure Timestamp: An integer indicating the departure time of a
   packet.

   QUIC SHOULD carry the TIMESTAMP Frame in each packet.

4.6.4.  ACK Delay Redefinition

   The ACK Delay field is carried in the ACK Frame.  Currently, the QUIC
   receiver reports ACK delays for only the largest acknowledged packet
   in an ACK frame, hence an RTT sample is generated using only the
   largest acknowledged packet in the received ACK frame.  For a more
   accurate RTTmin estimate when sending fewer ACK frames, QUIC SHOULD
   adopt the OWD-based RTTmin estimation.  The OWD-based RTTmin
   estimation requires the QUIC receiver to filter the departure
   timestamp for the packet that achieves the minimum OWD during the
   interval between two ACK frames and report the ACK delay of this
   packet.  Whether redefining the meaning of ACK delay or not, it
   depends on the negotiation between endpoints of the QUIC connection.

   In other words, QUIC SHOULD change the way of computing ACK Delay
   according to the arrival timestamp of the packet with minimum OWD
   instead of the arrival timestamp of the largest acknowledged packet.

5.  Security Considerations

   TBD

6.  IANA Considerations

   The value for ack-intensity-support transport parameter and ACK-
   INTENSITY frame should be allocated.

7.  References

7.1.  Normative References

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   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <https://www.rfc-editor.org/info/rfc1122>.

   [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>.

   [RFC3449]  Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M.
              Sooriyabandara, "TCP Performance Implications of Network
              Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
              December 2002, <https://www.rfc-editor.org/info/rfc3449>.

   [RFC4341]  Floyd, S. and E. Kohler, "Profile for Datagram Congestion
              Control Protocol (DCCP) Congestion Control ID 2: TCP-like
              Congestion Control", RFC 4341, DOI 10.17487/RFC4341, March
              2006, <https://www.rfc-editor.org/info/rfc4341>.

   [RFC5681]  Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
              Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
              <https://www.rfc-editor.org/info/rfc5681>.

   [RFC5690]  Floyd, S., Arcia, A., Ros, D., and J. Iyengar, "Adding
              Acknowledgement Congestion Control to TCP", RFC 5690,
              DOI 10.17487/RFC5690, February 2010,
              <https://www.rfc-editor.org/info/rfc5690>.

   [RFC6298]  Paxson, V., Allman, M., Chu, J., and M. Sargent,
              "Computing TCP's Retransmission Timer", RFC 6298,
              DOI 10.17487/RFC6298, June 2011,
              <https://www.rfc-editor.org/info/rfc6298>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [RFC9002]  Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
              and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
              May 2021, <https://www.rfc-editor.org/info/rfc9002>.

7.2.  Informative References

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   [ACK-PULL] Gomez, C., Ed. and J. Crowcroft, Ed., "TCP ACK Pull", Work
              in Progress, Internet-Draft, draft-gomez-tcpm-ack-pull-01,
              4 November 2019, <https://datatracker.ietf.org/doc/html/
              draft-gomez-tcpm-ack-pull-01>.

   [AOD]      Li, T., Zheng, K., and K. Xu, "Acknowledgment On Demand
              for Transport Control", IEEE Internet
              Computing 25(2):109-115, 2021.

   [IYENGAR-ACK]
              Iyengar, J., Ed. and I. Swett, Ed., "Sender Control of
              acknowledgment Delays in QUIC", Work in Progress,
              Internet-Draft, draft-iyengar-quic-delayed-ack-02, 2
              November 2020, <https://datatracker.ietf.org/doc/html/
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Authors' Addresses

   Tong Li
   Renmin University of China
   Room 421, Information Building, Renmin University of China

Li, et al.                 Expires 12 May 2023                 [Page 12]
Internet-Draft           Optimizing ACK in QUIC            November 2022

   Haidian District
   Beijing
   China
   Email: tong.li@ruc.edu.cn

   Kai Zheng
   Huawei
   Information Road, Haidian District
   Beijing
   China
   Email: kai.zheng@huawei.com

   Rahul Arvind Jadhav
   Huawei
   D2-03,Huawei Industrial Base
   Longgang District
   Shenzhen
   China
   Email: rahul.jadhav@huawei.com

   Jiao Kang
   Huawei
   D2-03,Huawei Industrial Base
   Longgang District
   Shenzhen
   China
   Email: kangjiao@huawei.com

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