Internet DRAFT - draft-xie-tcpm-mptcp-feedback

draft-xie-tcpm-mptcp-feedback







TCP Maintenance and Minor Extensions (tcpm)                      B. Zhao
Internet-Draft                                                   W. Yang
Intended status: Standards Track                                   W. Du
Expires: 18 April 2024                                            Y. Ren
                                                                 X. Zhou
                                                                  G. Xie
                                                                    CNIC
                                                         16 October 2023


                  A Message Feedback Method for MPTCP
                    draft-xie-tcpm-mptcp-feedback-00

Abstract

   Mobile phone devices are usually configured with multiple wireless
   access network cards, such as LTE/5G, Wi-Fi.  And the wireless
   network is a network with highly time-varying bandwidth.  For a
   single wireless device, the limited bandwidth cannot meet the peak
   rate requirements of low-latency applications.  MPTCP supports the
   simultaneous use of multiple networks on mobile devices.  Due to the
   time-varying nature of wireless networks, it is challenging for MPTCP
   to accurately schedule data blocks to different sub-streams to meet
   their low-latency requirements.  This document proposes a new cross-
   layer feedback method for wireless networks to pass the scheduling
   information and status of the wireless network to the MPTCP Server.
   MPTCP Server can predict the transmission capacity of the wireless
   network based on this cross-layer information, thereby improving the
   efficiency of data block scheduling on multipaths.

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
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   This Internet-Draft will expire on 18 April 2024.





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Copyright Notice

   Copyright (c) 2023 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/
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Design Overview . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Non-3GPP Device Information . . . . . . . . . . . . . . . . .   4
   5.  3GPP Device Information . . . . . . . . . . . . . . . . . . .   4
   6.  MP_INFO Usage . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Historical Note  . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   With the popularity of mobile devices, most devices have multiple
   wireless access methods, such as 5G, and Wi-Fi.  This has brought a
   realistic basis for the popularity of MPTCP.  However, the current
   MPTCP can only perceive information such as RTT, but cannot perceive
   information from edge wireless devices.  Therefore, a new subtype of
   MPTCP options is proposed in this document to transmit cross-layer
   information of wireless devices [RFC8684].  Figure 1 illustrates the
   integration of the MP_INFO into the wireless devices, where the MPTCP
   client resides on the UE and the MPTCP server resides on the Server.










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   +---------+    +---------+         +--------+          +----------+
   |         |    |    NR   |  GTP-U  |        | MP_INFO  |          |
   |         |----+---------|---------|   UPF  |----------|          |
   |    UE   |    |  3GPP   |         |        |          |   Server |
   |---------|    +---------+         +--------+          |--------- |
   |  MPTCP  |    +---------+                             |   MPTCP  |
   |         |    |         |       MP_INFO               |          |
   |         |----|Non-3GPP |-----------------------------|          |
   |         |    |         |                             |          |
   +---------+    +---------+                             +----------+

                 Figure 1: A network architecture for MPTCP

2.  Terminology

   NR:  New Radio, a new wireless access technology for 5G.

   GTP-U Message:  GTP-U (user plane) messages are either user plane
      messages or signalling messages.  User plane messages are used to
      carry user data packets between GTP-U entities.  Signalling
      messages are sent between network nodes for path management and
      tunnel management.GTP-U peer: node implementing at least one side
      of any of the GTP user plane based protocols.

   UPF:  User Plane Function.

   CQI:  CQI reflects the time-changing link capability.

3.  Design Overview

   In mobile networks, the performance of wireless devices has a great
   impact on data transmission.  Therefore, by feeding back the
   information of the wireless device to the MPTCP server, it is
   convenient for the MPTCP scheduler to schedule traffic to different
   paths according to the information of the edge device.  For the non-
   3GPP path, the Wi-Fi AP can directly modify the MPTCP data packet to
   feed back the device information to the MPTCP server.  For the 3GPP
   path, 5G NR periodically feeds back equipment information to UPF
   through the GTP-U protocol [GTP-U].  UPF can directly modify the
   MPTCP data packet to feed back the device information to the MPTCP
   server.  This document defines the extension of the MPTCP subtype,
   which allows the MPTCP server schedules traffic to different paths
   according to the information of edge devices.  In addition, this
   document provides a cross-layer information transfer method for 3GPP
   and non-3GPP equipment [_5G-MPTCP].  Section 4 will introduce the
   transmission method of non-3GPP devices.  In Section 5, the
   transmission method of 3GPP equipment will be introduced.  Section 6
   will introduce the usage of MP_INFO.



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4.  Non-3GPP Device Information

   The MPTCP server needs to obtain information on non-3GPP devices,
   such as Wi-Fi AP.  This document defines a new MPTCP Option subtype
   MP_INFO.  Non-3GPP devices can transform devices information from
   wireless devices to the MPTCP server.  The format of MP_INFO is shown
   in Figure 2.  It has the following fields:

   Device Type:  The type of device, 0x1 represents the non-3GPP path.

   Rate:  The send Rate of non-3GPP devices.

   Buffer Length:  The buffer length of a non-3GPP device.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Kind     |     Length    |Subtype|Device.|    Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Rate                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Buffer Length                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: MP_INFO Structure for Non-3GPP Device

5.  3GPP Device Information

   For the 3GPP path, we need to overcome the difficulty of acquiring 5G
   NR information.  In the 3GPP path, the GTP-U tunnel is responsible
   for transmitting data between the radio access network and the
   UPF[gNB].  So as shown in Figure 3, for the 3GPP path, 5G NR
   transmits equipment information to UPF through GTP-U [GTP-U].  Then,
   UPF transmits the calculated rate and Buffer to the MPTCP server
   through MP_INFO.  In the 3GPP path, the GTP-U tunnel is responsible
   for transmitting data between the radio access network and the
   UPF[gNB]. 5G NR uses the GTP-U tunnel to periodically send status
   information to the UPF, e.g. 1 ms. 5G NR only transmits the key
   information that affects the latency.  Note that this information is
   only transmitted between 5G NR and UPF.

   +---------+    +---------+          +---------+           +---------+
   |   UE    |    |    NR   |   GTP-U  |   UPF   |  MP_INFO  |  Server |
   +---------+----+---------|----------|---------|-----------|---------|
   |  MPTCP  |    |         |          |         |           |   MPTCP |
   +---------+    +---------+          +---------+           +---------+

             Figure 3: Communication process between NR and UPF



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   The format of MP_INFO for 3GPP devices is shown in Figure 4.  It has
   the following fields:

   Device Type:  The type of device, 0x2 represents the 3GPP path.

   Rate:  The send rate of the 3GPP device, can be calculated by CQI.

   RLC Buffer:  The sum of RLC buffer length, can be feedback through NR
      [RLC].

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Kind     |     Length    |Subtype|Device.|    Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Rate                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           RLC Buffer                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 4: MP_INFO Structure for 3GPP Device

6.  MP_INFO Usage

   MPTCP scheduler can leverage cross-layer information from 5G NR and
   Wi-Fi AP to predict the transmission delay of data blocks on each
   path.  However, there is a visual gap between this cross-layer
   information and the MPTCP server, which requires different methods on
   different paths to transmit cross-layer path information to the MPTCP
   server.  So this document separately introduces the cross-layer
   information collection for non-3GPP and 3GPP paths.  For 3GPP paths,
   we recommend feeding back the MP-INFO option every 10ms.  Because
   3GPP equipment generally uses fixed time slot allocation, the time of
   one frame is 10ms.  Non-3GPP devices do not have fixed time slots, so
   the feedback time can be flexible.

   And network operator can design their prediction delay methods
   according to the cross-layer information.  By leveraging cross-layer
   information from edge wireless, the MPTCP server can predict downlink
   latency and optimize multipath scheduling.  For example, By CQI and
   RLC Buffer information, the MPTCP server can predict the delay of the
   3GPP path.  By Rate and Buffer Length information, UPF can predict
   the delay of the non-3GPP path.  According to the predicted
   transmission delay, the MPTCP scheduler can use different strategies
   to schedule packets.






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   MP-INFO option is an incremental information.  In multipath, some
   paths may do not support this option.  For this case, the MPTCP
   scheduler can fall back to the MinRTT scheduler.

7.  IANA Considerations

   This draft adds the following subtype numbers to the MPTCP Option
   Subtypess registry of [RFC8684]:

         +=======+=========+=========================+===========+
         | Value | Symbol  | Name                    | Reference |
         +=======+=========+=========================+===========+
         |   0x9 | MP_INFO | Cross layer information | [RFC8684] |
         |       |         | of non-3GPP devices     |           |
         +-------+---------+-------------------------+-----------+

                       Table 1: MPTCP Option Subtypes

                   +===================+===============+
                   | Device Type Value | Message       |
                   +===================+===============+
                   |               0x1 | Non-3GPP Path |
                   +-------------------+---------------+
                   |               0x2 | 3GPP Path     |
                   +-------------------+---------------+

                      Table 2: Device Type in MP_INFO

8.  Security Considerations

   Since the MP_INFO option requires intermediate devices to modify data
   packets, some devices may not support this option.

   Some wireless devices may send incorrect MP-INFO information, so the
   terminal should confirm the security of the path.

9.  References

9.1.  Normative References

   [RFC8684]  Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
              Paasch, "TCP Extensions for Multipath Operation with
              Multiple Addresses", RFC 8684, DOI 10.17487/RFC8684, March
              2020, <https://www.rfc-editor.org/info/rfc8684>.

9.2.  Informative References





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   [gNB]      3GPP TS 38.300 (2023-06), "NR and NG-RAN Overall
              description (Release 15)", n.d..

   [GTP-U]    3GPP TS 29.281 V18.0.0 (2023-06), "General Packet Radio
              System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)
              (Release 18)", n.d..

   [RLC]      3GPP TS 38.322 (2023-06), "Radio Link Control (RLC)
              protocol specification (Release 15)", n.d..

   [_5G-MPTCP]
              3GPP, "System architecture for the 5G System (5GS) Release
              17", 2022.

Appendix A.  Historical Note

Authors' Addresses

   Baosen Zhao
   CNIC
   Beijing
   100083
   China
   Email: zhaobaosen@cnic.cn


   Wanghong Yang
   CNIC
   Beijing
   100083
   China
   Email: yangwanghong@cnic.cn


   Wenji Du
   CNIC
   Beijing
   100083
   China
   Email: hjdu@cnic.cn


   Yongmao Ren
   CNIC
   Beijing
   100083
   China
   Email: renyongmao@cstnet.cn



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   Xu Zhou
   CNIC
   Beijing
   100083
   China
   Email: zhouxu@cstnet.cn


   Gaogang Xie
   CNIC
   Beijing
   100083
   China
   Email: xie@cnic.cn





































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